In humans, noroviruses (NVs) cause acute epidemic and viral gastroenteritis. NVs do not only infect humans; viruseshave also been found in pigs, cows, sheep, mice and dogs. The focus in this project has been on the murine norovirus(MNV). MNV is a member of the viral family Caliciviridae and it consists of a single-stranded, positive sense RNAgenome. The genome includes three open reading frames (ORFs), ORF1 encodes for a polyprotein that consists of theprecursor to the 6-7 non-structural (NS) proteins. The polyprotein is cleaved by the NS6 protease. The NS6 isresponsible for all the cleaving in ORF1 and that makes it an attractive target for antiviral drugs. The NS6 proteinstructure has been determined at 1.66 Å resolution using X-ray diffraction techniques. Surprisingly, the electrondensity map revealed density for a peptide bound in the active site. The peptide had a length of 7 residues andoriginated from the C-terminus of another chain in an adjacent asymmetric unit. The active site triad was composed ofthe conserved residues; histidine 30, aspargine 54 and cysteine 139, however in the structure the cysteine 139 ismutated to an alanine to inactivate the protease. Activity assays were performed to probe the importance of the residuein position 109 in the β-ribbon located close to the active site. The three full-length constructs with the mutations;I109A, I109S and I109T were found to have less activity than the full-length wt (1-183). A truncated protease, lacking9 residues in the C-terminus, also had less activity. This indicates that the terminal residues are also important foractivity.

Reverse micelles systems AOT/isooctane was used for the concentration chymotrypsin from crude aqueous extract of red perch (intestine). The effects of pH and AOT concentration in the forward extraction step and pH and KCl concentration in the backward extraction step on the enzyme activity, purification fold and recovery yield were studied. The optimum conditions for the forward extraction were AOT concentration 20 mM and pH of 7.0 and optimum conditions for backward extraction were KCl concentration 1.0 M and pH of 7.5 which gave a good recovery yield (102.24%) and a purification (32.24-fold). The addition of 15% v/v alcohol in backward extraction dramatically improved recovery yield by 4.5 times and purification by 2.5 times. The enzyme activity and recovery yield obtained using reverse micelles method under its optimal conditions were 2 fold higher than those obtained using the ammonium sulphate precipitation method, while purification fold were 3 fold higher. / Fish processing waste can be used to produce commercially valuable by-products, such as chymotrypsin which has application in various industries including the food industry, leather production industry and chemical industry. My project is to produce valuable by-products from the fish processing.

This thesis examines the synthesis of α-fluoro-β-amino acids, and the influence of the constituent fluorine on the conformation and biological properties of β-peptide derivatives. Chapter One discusses the unique properties of the C-F bond, and applications of fluorine substitution in organic and medicinal chemistry. This is followed by a review of fluorinated analogues of α-amino acids, and how their incorporation into α-peptides has resulted in profound modifications, such as enhanced thermal and chemical stability, increased affinity for lipid bilayers, stronger self-association and improved biological activity. Experimental and theoretical data indicate two conformational effects associated with fluoroamides: the F-C-C(O)-N(H) moiety in α-fluoroamides adopts an antiperiplanar conformation, and in N-β-fluoroethylamides a gauche conformation between the vicinal C-F and C-N(CO) bonds is favoured. Chapter Two details the synthesis of a series of fluorinated β-peptides (2.13-2.24) designed to investigate the use of these stereoelectronic effects to control the conformation of β-peptide bonds. X-ray crystal structures were obtained for seven of these compounds and revealed the compounds had the expected conformations: when fluorine was positioned β to a nitrogen a gauche conformation was observed, and when fluorine was positioned α to a C=O group the structure adopted an antiperiplanar conformation. Thus, the strategic placement of fluorine can control the conformation of β-peptide bonds, and hence could be used to direct the secondary structures of β-peptides. The chapter is prefaced by an introduction to β-amino acids and the secondary structures of β-peptides. Chapter Three outlines the stereoselective synthesis of a series of α-fluorinated-β-amino acids. The synthesis of α-fluoro-β3-amino acids was achieved via direct fluorination of β3-amino acids with LDA and NFSI. The fluorination of N-Boc-protected β3-homophenylalanine, β3-homoleucine, β3-homovaline and β3-homoalanine all proceeded with good diastereomeric excesses (> 85 % de). However, the fluorination of N-Boc-protected β3-homophenylglycine occurred with a lower diastereomeric excess of 66%. Replacement of the Boc amine protecting group of β3-homophenylglycine with Cbz and Bz groups did not alter the stereoselectivity of the fluorination reaction, and substitution with an acetyl amine protecting group reduced the diastereomeric excess to 26%. The stereoselective synthesis of an α-fluoro-β2-homophenylalanine from 3-phenylpropanoic acid is also detailed. Conversion of the acid to the Evan's oxazolidinone followed by enantioselective fluorination and alkylation in high diastereomeric excess, and subsequent amination gave the α-fluorinated β2-amino acid. Chapter Four describes the enzyme assays carried out to assess the inhibitory activity of α-fluoro-β-amino acids, and the analogous non-fluorinated β-amino acids, against α-chymotrypsin. Both fluorinated and non-fluorinated β-amino acid derivatives were found to be competitive inhibitors of α-chymotrypsin, with Ki values in the low millimolar range. The fluorinated β2-homophenylalanine and β3-homophenylglycine derivatives (2.35, 3.26a, 3.43a and 3.44) were found to be more active against α-chymotrypsin than their non-fluorinated analogues (5.27, 3.24, 3.40 and 3.41), whereas the fluorinated β3-homophenylalanine methyl ester (2S,3S)-2.49 was inactive against α-chymotrypsin although the corresponding non-fluorinated derivative (S)-3.28 was a potent inhibitor. In Chapter Five a series of N-succinyl-β-amino acids-p-nitroanilides (5.8-5.13), containing both fluorinated and non-fluorinated β-amino acids, were designed and synthesised as possible substrates of α-chymotrypsin. β-Peptides are stable towards proteolytic hydrolysis, but the introduction of fluorine at the α-position in a β-amino acid was proposed to increase the activity of the adjacent amide bond, and thus make the β-peptide more susceptible to protease cleavage. However, the incorporation of fluorine had no influence on the proteolytic stability of compounds 5.8-5.13 as they were all found to be stable towards hydrolysis by α-chymotrypsin. Compounds 5.8, 5.9 and 5.13 were established as reversible competitive inhibitors of α-chymotrypsin Chapter Six is an experimental chapter and outlines the synthesis, purification and characterisation of the compounds prepared in this thesis.

Orientador: Flavia Maria Netto / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-06T03:08:28Z (GMT). No. of bitstreams: 1 Souza_AparecidaSoniade_M.pdf: 22255615 bytes, checksum: b4f416e6c5d3d387d2cf067d397f7f13 (MD5) Previous issue date: 2000 / Resumo: o presente trabalho teve como objetivo estudar o comportamento de isolados protéicos de soja (IPSs) sujeitos a diferentes tratamentos térmicos quando submetidos à hidrólise, com uso da enzima a-quimotripsina e comparar os peptídeos obtidos desta hidrólise. Para tanto, produziu-se IPS a partir da farinha desengordurada de soja (FDS). Este isolado, denominado de IPS nativo (IPSn) foi então submetido à temperaturas de 70, 80 e 90°C por 10 minutos, com objetivo de obter isolados com diferentes graus de desnaturação. Determinou-se a composição centesimal da FDS e IPSn. Para os isolados protéicos de soja nativo (IPSn) e tratados termicamente (IPSsTT) determinou-se o teor de fitato, atividade dos inibidores de tripsina (IT) e o índice de dispersibilidade de proteína (IDP). O perfil das proteínas foi analisado por eletroforese em gel de poliacrilamida na presença de dodecil sulfato de sódio (SDS-PAGE) e por cromatografia líquida de exclusão molecular de alta eficiência (SE-HPLC) e o grau de desnaturação, por calorimetria diferencial de varredura (DSC). A reação de hidrólise foi monitorada pelo método pH-stat e foi interrompida ao atingir 4,5% de grau de hidrólise (GH). Os hidrolisados obtidos foram analisados por eletroforese em SDS-P AGE e por SE-HPLC. O tratamento térmico não influenciou no conteúdo de fitato dos IPSsTT, mas a atividade do inibidor de tripsina e o IDP diminuíram significativamente. A análise DSC mostrou mudanças conformacionais nas proteínas das frações 7S e 11S. O comportamento eletroforético não apresentou diferenças entre o IPS nativo e os tratados termicamente ...Observação: O resumo, na íntegra poderá ser visualizado no texto completo da tese digital. / Abstract: The objective of this research was to study the behaviour of heat treated soy protein isolates (SPIs) when submitted to enzymatic hydrolysis with achymotrypsin and to analyse the products of hydrolysis. Native soy protein isolate (SPIn) was produced from defatted soy flour (DSF). The SPIn was then submitted to temperatures of 70, 80 and 90°C for 10 minutes, aiming at obtaining isolates with different degrees of denaturation. The proximate compositions of the DSF and the SPIn were determined. For SPIn and the heat treated soy protein isolates (HTSPIs), the phytate content, trypsin inhibitor activity (TI) and dispersibility index (DPI) were determined. The protein profile was analysed by gel electrophoresis in polyacrylamide gel, in the presence of sodium dodecyl sulphate (SDS-PAGE) and by size exclusion high performance liquid chromatography (SE-HPLC), and the degree of denaturation by differential scanning calorimetry (DSC). The heat treatment had no effect on the phytate content of the (HISPIs), but the trypsin inhibitor activity and DPI significantly decreased ...Note: The complete abstract is available with the full electronic digital thesis or dissertations. / Mestrado / Nutrição Aplicada a Tecnologia de Alimentos / Mestre em Ciência da Nutrição

No description available.

Digestion of proteins in the midgut of lepidopteran larvae relies on different types of peptidases, among the trypsins and chymotrypsins. In this work four chymotrypsinlike peptidases (MsCTLP1–4) were identified from the larval midgut of M. sexta, which are distantly related to another chymotrypsin (MsCT), a previously described peptidase present in the larval midgut of M. sexta. MsCTLP1–4 fit perfectly into a novel subgroup of insect CTLPs by sequence similarity and by the replacement of GP by SA in the highly conserved GDSGGP motif. Examination of MsCTLP expression in different tissues showed that most of the peptidases were predominantly expressed in the anterior and median midgut, while some were found in the Malpighian tubules. Expression analysis of MsCTLPs at different physiological states revealed that the mRNA amounts did not differ considerably in feeding and starving larvae except for MsCTLP2, whose mRNA dropped significantly upon starvation. During molting, however, the mRNA amounts of all MsCTLPs dropped significantly. Immunological determination of MsCTLP1 amounts showed that the mature peptidase was only detectable in the gut lumen of feeding and re-fed larvae, but not in that of starving or molting larvae, suggesting that MsCTLP1 secretion is suspended during starvation or molt. Differential regulation of transcript levels as well as their partial expression in Malpighian tubules might point to a role, which is distinct from digestion for at least some MsCTLPs. In line with this assumption, MsCTLP1 was shown to interact with the chitin synthase 2 (MsCHS2), necessary for chitin synthesis in the course of peritrophic matrix formation in the midgut of M. sexta. The occurrence of this interaction in vivo is supported by colocalization and co-immunoprecipitation. The data suggest that chitin synthesis is controlled by an intestinal proteolytic signaling cascade linking chitin synthase activity to the nutritional state of the larvae. As MsCTLP1 appears to be involved in such signaling cascades, other midgut peptidases could have other targets and may therefore regulate different activities. To gain more insight into the functions of CTLPs, the gene family encoding these peptidases in the genome of the red flour beetle, T. castaneum, was analyzed. Using an extended search pattern, 14 TcCTLP genes were identified that encode peptidases with S1 specificity pocket residues typically found in chymotrypsin-like enzymes. Analysis of the expression patterns of seven TcCTLP genes at various developmental stages revealed that some TcCTLP genes were exclusively expressed in feeding larval and adult stages (TcCTLP-5A/B, TcCTLP-6A). Others were also detected in non-feeding embryonic (TcCTLP-5C, TcCTLP-6D) and pupal stages (TcCTLP-5C, TcCTLP- 6C/D/E). TcCTLP genes were expressed predominantly in the midgut where they presumably function in digestion. However, TcCTLP-5C and TcCTLP-6C also showed considerable expression in the carcass. The latter two genes might therefore encode peptidases that act as molting fluid enzymes. To test this hypothesis, western blots were performed using protein extracts from larval exuviae. The extracts reacted with antibodies to TcCTLP-5C and TcCTLP-6C suggesting that the corresponding peptidases are secreted into the molting fluid. Finally, systemic RNAi experiments were performed. While injections of dsRNAs to TcCTLP-5A/B and TcCTLP-6A/D/E into penultimate larvae did not affect growth or development, injection of dsRNA for TcCTLP-5C and TcCTLP-6C resulted in severe molting defects. Recombinant expressed TcCTLP-5C2 was moreover activated by trypsin and was able to hydrolyze AAPF, hence making TcCTLP-5C the first described chymotrypsin-like peptidase ever to be involved in molting.

Tripsinas e quimotripsinas são classes de serina peptidases amplamente estudadas e fortemente responsáveis pela digestão proteica, pela clivagem de ligações peptídicas no lado carboxila de L-aminoácidos de cadeia lateral básica e hidrofóbica, respectivamente. Três processos regulam finamente a ação dessas peptidases: secreção, ativação do precursor (zimogênio) e o sítio de reconhecimento do substrato. No presente trabalho é apresentada uma análise filogenética detalhada das tripsinas e quimotripsinas de três ordens de insetos holometábolos, revelando características divergentes nas enzimas de Lepidóptera em relação a Coleóptera e Díptera. Em particular, o sub-sítio S1 das tripsinas foi observado como mais hidrofílico em Lepidóptera do que em Coleóptera e Díptera, enquanto os sub-sítios S2-S4 parecem mais hidrofóbicos, sugerindo diferente preferências pelo substrato. Além disso, Lepidóptera mostrou um grupo de tripsinas bastante específico a um grupo taxonômico, compreendendo somente proteínas de espécies da família Noctuidae. Evidências de eventos de auto-ativação facilitada foram também observadas em todas as ordens de insetos estudadas, com as características do motivo de ativação do zimogênio complementárias ao sítio ativo das tripsinas. Em contraste, as quimotripsinas de insetos não parecem ter uma história evolutiva peculiar com respeito a, por exemplo, seus homólogos em mamíferos. Em geral, os presentes resultados sugerem que a necessidade de uma rápida taxa de autoativação fez os insetos holometábolos selecionarem grupos especializados de tripsinas com altas taxas de auto-ativação e também destacam que a evolução das tripsinas culminou em um grupo especializado de enzimas em Lepidóptera. / Trypsins and chymotrypsins are well-studied classes of serine peptidases largely responsible for the digestion of proteins by cleavage of the peptide bond at the carboxyl side of basic and hydrophobic L-amino acids, respectively. Three processes mainly regulate the action of these peptidases: secretion, precursor (zymogen) activation and substrate-binding site recognition. In the present work is presented a detailed phylogenetic analysis of trypsins and chymotrypsins in three orders of holometabolous insects revealing divergent characteristics in the Lepidoptera enzymes in relation to Coleoptera and Diptera. In particular, trypsin subsite S1 was observed to be more hydrophilic in Lepidoptera than in Coleoptera and Diptera, whereas subsites S2-S4 appeared more hydrophobic, suggesting different substrate preferences. Furthermore, Lepidoptera displayed a very specific taxonomic trypsin group, only encompassing proteins from the Noctuidae family. Evidences for facilitated trypsin auto-activation events were also observed in all the insect orders at hand, with the characteristic zymogen activation motif complementary to the trypsin active site. In contrast, insect chymotrypsins did not seem to have a peculiar evolutionary history with respect to e.g. their mammal counterparts. Overall, the present findings suggest that the need for fast digestion made holometabolous insects evolve specialized groups of trypsins with high autoactivation rates and highlight that the evolution of trypsins culminated in a specialized group of enzymes in Lepidoptera.

by Ricardo Wong Chi Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 128-138). / Abstracts in English and Chinese. / Acknowledgments --- p.i / Abstract --- p.ii / 論文摘要 --- p.iv / Table of Contents --- p.vi / List of Figures --- p.xi / List of Tables --- p.xiii / List of Abbreviations --- p.xiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Overview of Serine Protease Inhibitors --- p.1 / Chapter 1.2 --- Classification of Serine Protease Inhibitors --- p.2 / Chapter 1.2.1 --- Kunitz Type Serine Protease Inhibitors --- p.7 / Chapter 1.2.2 --- Bowman-Birk Type Serine Protease Inhibitors --- p.11 / Chapter 1.2.3 --- Squash Type Serine Protease Inhibitors --- p.16 / Chapter 1.3 --- Role of Serine Protease Inhibitors in Plants --- p.20 / Chapter 1.4 --- Nutritional Fact of Serine Protease Inhibitors --- p.22 / Chapter 1.5 --- Possible Applications of Serine Protease Inhibitors --- p.25 / Chapter 1.5.1 --- Medical Applications --- p.25 / Chapter 1.5.2 --- Agricultural Applications --- p.29 / Chapter 1.6 --- Rationale of the Present Study --- p.31 / Chapter Chapter 2 --- Screening of Seeds for Inhibitory Activities Against Serine Proteases --- p.33 / Chapter 2.1 --- Introduction --- p.33 / Chapter 2.2 --- Materials and Methods --- p.37 / Chapter 2.2.1 --- Materials --- p.37 / Chapter 2.2.2 --- Extraction Method --- p.37 / Chapter 2.2.3 --- Assays for Proteases Inhibitory Activities --- p.38 / Chapter 2.2.3.1 --- Assay for Chymotrypsin Activity --- p.38 / Chapter 2.2.3.2 --- Assay for Trypsin Activity --- p.38 / Chapter 2.2.3.3 --- Assay for Elastase Activity --- p.39 / Chapter 2.2.3.4 --- Assay for Subtilisin Activity --- p.39 / Chapter 2.2.3.5 --- Assays for Protease Inhibitory Activities --- p.40 / Chapter 2.2.4 --- Determination of Protein Concentration --- p.41 / Chapter 2.3 --- Results --- p.42 / Chapter 2.3.1 --- Extraction --- p.42 / Chapter 2.3.2 --- Serine Proteases Inhibitory Activities --- p.42 / Chapter 2.4 --- Discussion --- p.47 / Chapter Chapter 3 --- Isolation of Chymotrypsin Inhibitor and Trypsin Inhibitors from Momordica cochinchinensis Seeds --- p.49 / Chapter 3.1 --- Introduction --- p.49 / Chapter 3.2 --- Materials and Methods --- p.56 / Chapter 3.2.1 --- Materials --- p.56 / Chapter 3.2.2 --- Protein Extraction --- p.57 / Chapter 3.2.3 --- SP-Sepharose Chromatography --- p.57 / Chapter 3.2.4 --- Reversed Phase High Pressure Liquid Chromatography --- p.58 / Chapter 3.2.5 --- Assays for Chymotrypsin and Trypsin Inhibitory Activities --- p.60 / Chapter 3.2.6 --- Titration of Chymotrypsin --- p.61 / Chapter 3.2.7 --- Tricine Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis --- p.62 / Chapter 3.2.8 --- Coupling of Trypsin-Sepharose 4B Affinity Column --- p.63 / Chapter 3.2.9 --- Affinity Chromatography on Trypsin-Sepharose 4B --- p.64 / Chapter 3.3 --- Results --- p.65 / Chapter 3.3.1 --- SP-Sepharose Chromatography --- p.65 / Chapter 3.3.2 --- Reversed Phase High Pressure Liquid Chromatography --- p.67 / Chapter 3.3.3 --- Summary of Purification --- p.71 / Chapter 3.3.4 --- Titration of Chymotrypsin --- p.74 / Chapter 3.3.5 --- Tricine Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis --- p.74 / Chapter 3.3.6 --- Affinity Chromatography on Trypsin-Sepharose 4B --- p.78 / Chapter 3.4 --- Discussion --- p.81 / Chapter Chapter 4 --- Characterization of Chymotrypsin Inhibitor and Trypsin Inhibitors --- p.88 / Chapter 4.1 --- Introduction --- p.88 / Chapter 4.2 --- Materials and Methods --- p.90 / Chapter 4.2.1 --- Materials --- p.90 / Chapter 4.2.2 --- Determination of Molecular Weight --- p.90 / Chapter 4.2.3 --- Amino Acid Sequence Analysis --- p.91 / Chapter 4.2.4 --- Surface Plasmon Resonance Measurement --- p.92 / Chapter 4.2.4.1 --- Immobilization of Ligands on the Surface of Optical Biosensors --- p.92 / Chapter 4.2.4.2 --- Determination of Kinetics Constants --- p.93 / Chapter 4.2.4.3 --- pH Dependence of the Inhibition by Chymotrypsin Inhibitor --- p.93 / Chapter 4.2.4.4 --- Data Analysis --- p.94 / Chapter 4.2.5 --- Effect of Chymotrypsin Inhibitor on the Estereolytic Activity and Proteolytic Activity of Chymotrypsin --- p.95 / Chapter 4.2.6 --- Specificities of the Inhibitors % --- p.96 / Chapter 4.2.7 --- Binding Ratio of CI to Different Proteases --- p.97 / Chapter 4.2.8 --- Effects of the Proteases on Their Corresponding Inhibitors --- p.97 / Chapter 4.2.8.1 --- Tricine Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis --- p.97 / Chapter 4.2.8.2 --- Assay for Chymotrypsin Inhibitory Activity --- p.98 / Chapter 4.3 --- Results --- p.99 / Chapter 4.3.1 --- Molecular Weight of the Inhibitors --- p.99 / Chapter 4.3.2 --- N-terminal Amino Acid Sequence --- p.99 / Chapter 4.3.3 --- Surface Plasmon Resonance Measurement --- p.102 / Chapter 4.3.3.1 --- Kinetics of Chymotrypsin Inhibitor --- p.102 / Chapter 4.3.3.2 --- Kinetics of Trypsin Inhibitors --- p.106 / Chapter 4.3.3.3 --- pH Dependence of the Inhibition by Chymotrypsin Inhibitor --- p.106 / Chapter 4.3.4 --- Effect of Chymotrypsin Inhibitor on the Estereolytic Activity and Proteolytic Activity of Chymotrypsin --- p.106 / Chapter 4.3.5 --- Specificities of the Inhibitors --- p.110 / Chapter 4.3.6 --- Binding Ratio of CI to Different Proteases --- p.112 / Chapter 4.3.7 --- Effects of the Proteases on Their Corresponding Inhibitors --- p.112 / Chapter 4.4 --- Discussion --- p.119 / Chapter Chapter 5 --- Conclusion --- p.125 / References --- p.128

Serina endopeptidases de insetos, principalmente tripsinas e quimotripsinas, estão envolvidas na digestão inicial de proteínas. Genes codificadores para estas enzimas estão organizados em famílias multigênicas tendo expressão diferencial de acordo com a dieta do inseto, estando envolvidos no desenvolvimento de resistência a diferentes metabólitos secundários vegetais. Para uma melhor compreensão desta interação, fez-se necessário o isolamento destas enzimas para insetos de diferentes ordens, bem como a caracterização de suas especificidades por duas abordagens: (a) caracterização cinética dos subsítios componentes do sítio de ligação de tripsinas e quimotripsinas, utilizando diferentes substratos, modificadores químicos e inibidores e (b) estudos estruturais por modelagem molecular, clonagem, expressão e cristalização destas enzimas de insetos. Além disso, estudos evolutivos por análise de distância possibilitaram uma caracterização inicial da interação insetoplanta. Estas determinações permitiram verificar que tripsinas de insetos apresentam diferenças de especificidade tanto dentre as diferentes ordens de insetos quanto em relação às tripsinas de vertebrados, sendo que as tripsinas da ordem Lepidóptera apresentam troca de especificidade primária hidrolisando preferencialmente substratos P1 Lys. Foram também observadas diferenças de hidrofobicidade para os subsítios caracterizados sendo que estes apresentam hidrofobicidades crescentes segundo o grau de complexidade dos insetos na sua escala evolutiva. A troca de especificidade e o aumento da hidrofobicidade podem permitir a hidrólise dos inibidores vegetais protéicos. A análise das sequências de tripsinas de insetos por Neighbor Joining (NJ) compõe uma árvore de distâncias topologicamente semelhante à árvore de relações filogenéticas determinadas por morfologia. A sobreposição de estruturas pré -determinadas de tripsina complexada a diferentes inibidores permite a identificação de posições de interação enzima-inibidor que justificam a classificação em grupos distintos de enzimas sensíveis ou resistentes a presença de inibidores na dieta de insetos. Da mesma forma: a caracterização da especificidade das quimotripsinas de insetos permitiu a separação de grupos distintos de quimotripsinas. Estes grupos são sustentados pela substituição do resíduo 59 em insetos polífagos que alimentam-se de plantas que contêm cetonas naturais reativas. Estas caracterizações demonstram a importância de um estudo detalhado da especificidade de serina endopeptidases possibilitando o desenho de moléculas apropriadas para inibição destas e desenvolvimento de estratégias de controle de insetos. / Insect serine endopeptidases, mairily trypsin and chymotrypsin are involved in initial protein digestion. Genes that encode these proteins are members of complex multigene families and are differentially expressed according to insects diet , thus being involved with resistance to plant metabolites. Purification of trypsins from different insect orders and chymotrypsins, as well as, characterization of their specificity are essential to a better understanding of this interaction. Characterization relied on two approaches: (a) kinetic characterization of the binding subsities of trypsins and chymotrypsins using different substrates, chemical modification and inhibition assays and (b) study of protein structure by molecular modelling and cloning, expression and crystallization of these enzymes. Besides that, evolutionary studies performed through distance analysis, permitted the investigation of plantinsect interaction. These characterizations showed that insect trypsins, in terms of specificity, are quite different from vertebrate trypsins and among insect orders. Lepidopterans trypsins have a distinct primary specificity, since they hydrolyses preferentially P1 Lys substrates, and present a crescent subsite hydrophobicity, which is directly correlated with the evolutionary scale. Both, the specificity exchange and the crescent hydrophobicity can allow the hydrolysis of vegetal proteic inhibitors. The analysis of trypsin sequences in Neighbor-Joining (NJ) algorithm yield a distance tree that is coherent with morphological phylogenetic relationships. The superposition of predicted structures of trypsins-inhibitors complexes permits to observe amino acid residues of interaction between enzyme-inhibitor, which support the distinction of different groups between sensitive and insensitive trypsins to the presence of inhibitors on insect diet. Similarly, characterization of insect chymotrypsins according to their specificity allowed us to classify these enzymes into different groups. These groups are supported by residue 59 replacements in polyphagous insects, which feed on plants bearing natural reactive ketones. These studies show the irnportance of a detailed study of serine endopeptidases, which may help in the development of better insect control strategies.

Tripsinas e quimotripsinas, enzimas pertencentes à classe das serina proteinases, são as principais enzimas proteolíticas digestivas presentes no intestino médio de insetos de diversas ordens. Entretanto, enzimas de diferentes insetos possuem propriedades cinéticas distintas, sendo os motivos dessas diferenças especulados. Precipitações por sulfato de amônio das tripsinas de Tenebrio molitor, Diatraea saccharalis e Spodoptera frugiperda mostram que insetos Lepidópteros possuem serina proteinases mais hidrofóbicas, que foi confirmado através de cromatografias de interação hidrofóbica e da análise de acesso do solvente às superfícies protéicas em modelagens tridimensionais de seqüências. Tal fato está relacionado à formação de oligômeros e resistência a defesas de plantas. Inativações por TPCK mostram que quimotripsinas digestivas de S. frugiperda, inseto polífago, reagem duas ordens de grandeza mais lentamente e possui um deslocamento do pH ótimo de modificação em mais de uma unidade quando comparada com dos outros dois organismos, fato relacionado à resistência a cetonas presentes em diversas plantas. A tripsina digestiva de Periplaneta americana foi purificada e microsseqüenciada, resultando na seqüência VSPAFSYGTG e associada a um alérgeno (denominado PaTry), expresso nos cecos e na região anterior do ventrículo. O anticorpo anti-tripsina de M. domestica reconheceu apenas uma banda no intestino de P. americana e foi utilizado para imunocitolocalizar tripsinas nos tecidos epiteliais, demonstrando que esta é secretada por exocitose nos cecos e na região anterior do ventrículo, como esperado. Por último, a atividade majoritária de quimotripsina se localiza surpreendentemente na região posterior do ventrículo de M. domestica. Apesar disso, apenas 28% dessa atividade é perdida através das fezes, pois 31% da atividade enzimática se encontra firmemente aderida à membrana, e 41% na fração celular solúvel (associada ao glicocálice), sendo a atividade solúvel luminal correspondente a apenas 12%, indicando a existência de pelo menos duas espécies moleculares distintas, uma solúvel e uma aderida à membrana, comprovado inativações térmicas das duas atividades (solúvel e aderida à membrana) na presença e na ausência de Triton X-100, sendo que a atividade aderida à membrana apresentou uma maior meia vida com uma cinética de primeira ordem nos dois casos. Ensaio em gel demonstrou que o homogeneizado possui apenas uma banda de atividade quimotríptica de 30 kDa. A atividade solúvel majoritária foi purificada até a homogeneidade, apresentando uma banda de 30 kDa em SDS-PAGE, pH ótimo de 7,4 e é 90% inativada por TPCK 0,1 mM em pH 8,5 em 15 min. Ela prefere substratos contendo Phe em P1, apesar clivar substratos contendo Tyr e Leu. Uma seqüência contígua similar a quimotripsina foi obtida a partir de uma biblioteca de cDNA de intestino médio de M. domestica, formada por 71 ESTs (de 826 seqüências obtidas ao acaso), indicando que esta deve corresponder à atividade majoritária. Essa seqüência, denominada MdChy1, prediz uma proteína madura de 28.639,2 Da e foi clonada e expressa de maneira recombinante em E. coli BL21 (DE-3) Star, sendo utilizada para produção de anticorpos policlonais em coelhos, que reconheceram uma banda de 30 kDa no ventrículo anterior e posterior, mas não no médio. Esses anticorpos foram utilizados para imunomarcações e reconheceram proteínas no lúmem, nas microvilosidades e em pequenas vesículas do epitélio, demonstrando que a quimotripsina é secretada ao lúmem por exocitose e indicando que o MdChy1 corresponde à atividade majoritária de quimotripsina. Análises de expressão em M. domestica indicam a existência de dois conjuntos de serina proteinases digestivas, um expresso na região anterior e um segundo na região posterior do ventrículo. O MdChy1 é expresso na região posterior, local em que se encontra a atividade majoritária de quimotripsina. Uma reconstrução filogenética dos genes similares a quimotripsinas de Drosophila melanogaster e de M. domestica demonstram que a MdChy1 se agrupa com genes expressos no intestino médio, portanto, com função digestiva. / Trypsins and chymotrypsins, serine proteinases enzymes, are the major proteolytic activities present in the midgut of insects. However, enzymes obtained from different insects present different kinetic properties, and the reason for the differences are speculated. Trypsin precipitation of Tenebrio molitor, Diatraea saccharalis and Spodoptera frugiperda with ammonium sulfate showed that Lepidopteran insects possess serine proteinases with a higher superficial hydrophobicity than insects belonging to other orders, which may be associated to oligomerization of enzymes and resistance to inhibitors present in the food. This was confirmed by hydrophobic interaction chromatography and analysis of solvent access to serine proteinases surface. Moreover, inactivations of chymotrypsins by TPCK showed that S. frugiperda chymotrypsins react one order slower and has an optimum pH of modification more than 1 unit higher than chymotrypsins of D. saccharalis and T. molitor, which was related with the resistance of the enzyme to the presence of plant ketones, since S. frugiperda is a polyphagous organism. The digestive trypsin from Periplaneta americana midgut was purified microssequenced, resulting in the sequence VSPAFSYGTG, coincident to the MPA3 allergen (named PaTry), which is expressed in the caeca and anterior ventriculus. Western blot using M. domestica trypsin antisera recognized a single band, and immunohistochemical assays using this antisera showed that the P. americana trypsin is secreted by exocitosys in caeca and anterior ventriculus, which is coincident to the expression data. Although the major M. domestica chymotrypsin activity is present in the posterior ventriculus, only 28% of the activity is lost in feces, because 31% of activity is membrane-bound, and 41% is in the cellular soluble fraction (glycocalix-associated), and only 12% of total activity is soluble in the lumen, indicating the existence of at least two molecular species of chymotrypsins. Thermal inactivations of both activities (soluble and membrane-bound) showed that they may represent two different molecular enzymes, since the membrane-bound activity has a higher half-life than the soluble both in the presence and in the absence of Triton X-100. Both activities presented a linear first-order inactivation kinetic. In gel assays showed the presence of only one activity band in the midgut of 30 kDa. The major soluble activity was purified through one affinitychromatography, and active fractions presented a single 30 kDa band, a optimum pH of 7.4 and was 90% modified by TPCK 0.1 mM at pH 8.5 during 15 min. This enzyme preferentially cleaves substrates containing Phe residues in P1, although it cleaves substrates containing Tyr and Leu. A contig of a chymotrypsin-like sequence was randomly obtained from a cDNA library of M. domestica midguts from 71 ESTs (a total of 826 sequences), indicating that this sequence corresponds to the major activity present in the lumen. This sequence, named MdChy1, predicted a protein with 28639.2 Da which was cloned, recombinantly expressed in E. coli BL21 (DE-3) Star, this recombinant MdChy1 was used to raise polyclonal antibodies in rabbit. A western blot using this antisera recognised a single band in the anterior and posterior ventriculus, but not in the middle. Imunno-gold labeling of epithelium marked proteins in the lumen, at the microvilli and inside small vesicles, demonstrating that chymotrypsin is secreted through exocytosis in M. domestica and reinforcing that MdChy1 corresponds to the major chymotryptic activity found in the midgut. A semi-quantitative RT-PCR of M. domestica serine proteinase-like genes demonstrated that there are two set of genes, one expressed in the anterior and another in the posterior ventriculus, as visualized in western blot. MdChy1 is expressed in the posterior ventriculus, where the major chymotryptic activity is found. A phylogenetic reconstruction of Drosophila melanogaster chymotrypsin-like sequences and M. domestica chymotrypsins showed that MdChy1 branched with sequences expressed in midgut, thus coding proteins involved in digestion.