No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Understanding the structural basis of specificity and promiscuity of paralogous enzymes is important for deciphering molecular mechanisms and is a necessary step towards designing enzyme-specific modulators. The main objective of this thesis is to provide structural insights that relate protein local sequences to their observed binding and activity profiles through the study of two human protein families – cytosolic sulfotransferases (SULTs) and sirtuins (SIRTs). This was achieved by comparing the family-wide ligand binding fingerprints of these two enzyme families with the structural details of their corresponding enzyme-ligand co-crystal structures. The hSULT enzyme family was profiled against a focused library through binding and activity assays. This suggested a number of novel compounds that bind to the less well-characterized SULT members (SULT1C3 and SULT4A1), and revealed additional broad-spectrum hSULT inhibitors. Based on the profiling data, three enzyme/co-factor/ligand complex structures were solved using X-ray crystallography. The structure of SULT1C2•PAP(3'-phosphoadenosine 5'-phosphate)•pentacholorphenol(PCP) provided a rationale for a novel SULTs inhibition mechanism that depends on substrate acidity. The SULT1B1•PAP•resveratrol structure suggested that the hydrogen-bonding coordination of the 5-OH group on resveratrol is the structural determinant for the observed substrate preference towards resveratrol. SULT2A1•PAP•lithocholic acid(LCA) ternary complex structure confirms that the specificity of SULT2A1 for lithocholic acid derives from its high hydrophobicity in the substrate binding pocket. The same approach was used to interrogate the interaction of the sirtuins with their peptide substrates. The binding and enzymatic assays for human sirtuins have suggested that SIRT1 and SIRT2 are generally less discriminate against substrates while class IV sirtuins - SIRT6 and SIRT7 might be highly specific enzymes. Three different biochemical and kinetic assays showed that SIRT6-dependent histone deacetylation is about 1,000 times slower than for other highly active sirtuins. To understand the molecular basis for the specificity and low activity of SIRT6, I determined the first set of crystal structures for SIRT6 in complex with ADPr (ADP ribose) and the non-hydrolyzable analog of OAADPr (2’-O-acetyl-ADP ribose) – NAADPr (2’-N-acetyl-ADP ribose). The structures revealed human SIRT6 has unique structural features including a splayed zinc-binding domain, lacks a helix bundle and the conserved, highly flexible, NAD(+)-binding loop, which contribute to its observed biochemical behavior.

Understanding the structural basis of specificity and promiscuity of paralogous enzymes is important for deciphering molecular mechanisms and is a necessary step towards designing enzyme-specific modulators. The main objective of this thesis is to provide structural insights that relate protein local sequences to their observed binding and activity profiles through the study of two human protein families – cytosolic sulfotransferases (SULTs) and sirtuins (SIRTs). This was achieved by comparing the family-wide ligand binding fingerprints of these two enzyme families with the structural details of their corresponding enzyme-ligand co-crystal structures. The hSULT enzyme family was profiled against a focused library through binding and activity assays. This suggested a number of novel compounds that bind to the less well-characterized SULT members (SULT1C3 and SULT4A1), and revealed additional broad-spectrum hSULT inhibitors. Based on the profiling data, three enzyme/co-factor/ligand complex structures were solved using X-ray crystallography. The structure of SULT1C2•PAP(3'-phosphoadenosine 5'-phosphate)•pentacholorphenol(PCP) provided a rationale for a novel SULTs inhibition mechanism that depends on substrate acidity. The SULT1B1•PAP•resveratrol structure suggested that the hydrogen-bonding coordination of the 5-OH group on resveratrol is the structural determinant for the observed substrate preference towards resveratrol. SULT2A1•PAP•lithocholic acid(LCA) ternary complex structure confirms that the specificity of SULT2A1 for lithocholic acid derives from its high hydrophobicity in the substrate binding pocket. The same approach was used to interrogate the interaction of the sirtuins with their peptide substrates. The binding and enzymatic assays for human sirtuins have suggested that SIRT1 and SIRT2 are generally less discriminate against substrates while class IV sirtuins - SIRT6 and SIRT7 might be highly specific enzymes. Three different biochemical and kinetic assays showed that SIRT6-dependent histone deacetylation is about 1,000 times slower than for other highly active sirtuins. To understand the molecular basis for the specificity and low activity of SIRT6, I determined the first set of crystal structures for SIRT6 in complex with ADPr (ADP ribose) and the non-hydrolyzable analog of OAADPr (2’-O-acetyl-ADP ribose) – NAADPr (2’-N-acetyl-ADP ribose). The structures revealed human SIRT6 has unique structural features including a splayed zinc-binding domain, lacks a helix bundle and the conserved, highly flexible, NAD(+)-binding loop, which contribute to its observed biochemical behavior.

No description available.

Currently, an increasing attention is being paid to phytochemicals as one of the most widely used chemopreventive compounds, generally considered as health-promoting and safe. Flavonoids representing a large group of phytochemicals are present in many dietary supplements formulated from natural sources. The consumption of these concentrated phytochemicals has dramatically increased in the recent decade. It appears, however, that the ingestion of flavonoids might be associated with some adverse effects. Some flavonoids are known modulators of enzymes involved in phase I and phase II metabolism of xenobiotics biotransformation, thus their induction may result in an increase of carcinogen activation. In this study, the effects of selected flavonoid compounds -naphthoflavone, - naphthoflavone, myricetin, and dihydromyricetin, and carcinogens (BaP, PhIP) on phase II metabolism enzymes, sulfotransferases (SULT), have been investigated. To determine the induction of SULT, antibodies for their immunodetection have been developed. Peptide antigens derived from sequences of selected rat sulfotransferases rSULT1A1, 1B1, 1C1, 1C2, 1C1/2, 1E1, and 2A1, were used as KLH conjugates for hen immunization to obtain yolk anti-peptide antibody (IgY). Fractions of IgY were isolated from eggs yolks by simple...

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2006. / Härtill 5 uppsatser.

Made available in DSpace on 2015-07-22T20:49:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-27. Added 1 bitstream(s) on 2015-08-11T03:26:11Z : No. of bitstreams: 1 Publico-12806.pdf: 1520174 bytes, checksum: ef3fc7f7d5723098ec8ce9d05fe62187 (MD5) / Heparam sulfato (HS) é um glicosaminoglicano altamente modificados (GAGs) ligados a um core proteíco, formando os proteoglicanos de heparam sulfato (HSPGs). A estrutura do HS é caracterizada por padrões de modificações específicas, dependendo do tipo celular, da idade e do organismo. A estrutura das cadeias de açúcar do HS são importantes na modulação da atividade dos HSPGs. A biossíntese do HS é conservada a partir de nematóides até o homem, iniciando no sistema retículo endoplasmático / cis-Golgi, onde uma ligação de tetrassacarídeo é adicionado a um resíduo de serina do core proteíco do proteoglicano. Após a adição covalente de um resíduo de xilose pela xilosil transferase, três diferentes enzimas adicionam os resíduos de galactose-galactose-ácido glucurônico, constituindo assim a região de ligação, sendo este último passo essencial para o complexo de polimerases EXT1 e EXT2 acrescentarem unidades alternadas de ácido glucurônico (GlcA) e glucosamina N-acetilada (GlcNAc) na região não-reduzida da cadeia. Após esta etapa de polimerização, um conjunto de modificações ocorrem: Ndesacetilação / N-sulfatação da GlcNAc pela enzima bifuncional, glucosaminil N-desacetilase / N-sulfotransferase, epimerização do ácido glucurônico adjacente ao recente domínio N-sulfatado pela glucuronosil C5 epimerase, e por fim, 2, 3 e 6-O sulfatação por diferentes sulfotransferases com distribuição tecido e isoformas específicas. A regulação dessas reações, bem como o mecanismo de sulfatação, são mal compreendidos. Além da evidência fragmentada, existe uma interrogação sobre a sistemática das interações bioquímicas da maquinaria biossintética do HS. N-Desacetilase-Nsulfotransferase 1 (Ndst1) promove a catálise inicial das modificações do HS e Heparina (Hep), removendo os grupos acetil das unidades de Nacetiglucosamina com subseqüente sulfatação dos amino grupos livres. Utilizando uma biblioteca de Phage Display, selecionamos com sucesso dois peptídeos que interagem especificamente com a Ndst1, inibindo sua atividade de sulfatação. Inibidores da maquinaria biossintética dos GAGs são importantes ferramentas para o estudo deste evento, bem como, na alteração da composição das cadeias de açúcar do HS em modelos in vitro. Ainda, utilizando as ferramentas de molecular docking e dinâmica molecular, fomos capazes de estudar com detalhe o sítio catalítico da NDST de origem humana e decifrar a relevância da precisão catalítica dos resíduos limitantes através da fenda hidrofóbica, bem como, a sua significância para o reconhecimento e sulfatação do glicano. Além disso, nós determinamos o resíduo de aminoácido essencial para a ligação ao hNDST, Finalmente, utilizando ambas tecnologias de identificação multidimensional da proteína e imunohistoquímica, fomos capazes de demonstrar inicialmente a presença e a localização tecidual dos diferentes proteoglicanos em diferentes órgãos do gastrópode Achatina fulica. A. Fulica é um modelo vital para a caracterização da especificidade e o modo de ação das enzimas envolvidas na biossíntese dos GAGs, pois a estrutura do GAG acaram sulfato, encontrado somente neste organismo, contradiz a atual teoria biossintética. Além disso, pela análise proteômica das proteínas isoladas do Golgi da A. fulica, bem como, a imunohistoquímica das secções dos tecidos, detectamos a presença da maquinaria de biossíntese dos glicosaminoglicanos. Portanto, este estudo busca elucidar a atividade da NDST, além de, fornecer novas técnicas e abordagens originais para o estudo da biossíntese dos GAGs. / TEDE / BV UNIFESP: Teses e dissertações

In sea urchin development, cell fate specification appears by the 60-cell stage embryo when several embryonic territories are recognized: the small micromeres, the large micromeres which will generate primary mesenchyme cells, the vegetal2 layer that will give rise to pigment cells, immunocytes, and muscle cells, the vegetal1 layer, as well as the oral and aboral ectoderm. A Delta-Notch signaling event is required for the differential specification of mesodermal cells that will give rise to secondary mesenchyme cells (SMCs). SMCs produce four cell types: pigment cells, blastocoelar cells, circumesophageal muscle cells, and coelomic pouch cells. Pigment cells are the first to be specified. During primary invagination at the gastrula stage, eight pigment cell progenitors delaminate from the archenteron into the blastocoel. By the pluteus stage, approximately 30 pigment cells are embedded in the ectoderm. Pigment cells produce echinochrome, a napthoquinone pigment. Previously, several genes in the sea urchin embryo were isolated that are expressed specifically in pigment cell precursors during the blastula stage. The goal of this research was to characterize a subset of these genes, which are highly similar to: the polyketide synthase gene (Pks), a sulfotransferase gene (Sult), three different members of the flavin-containing monooxygenase gene family (Fmo), and the transcription factor glial cells missing (Gcm). Polyketide synthases (PKSs) are a large family of multifunctional proteins mainly found in bacteria, fungi, and plants. They are responsible for the biosynthesis of a variety of polyketide compounds including antibiotics and mycotoxins. In the sea urchin, SpPks is required for echinochrome biosynthesis. Flavin-containing monooxygenases (FMOs) are NADPH-dependent flavoproteins mainly found in bacteria, plants, and higher metazoan. They are responsible for catalyzing the oxidation of several compounds including the detoxification of xenobiotics and activation of numerous metabolites. It is known that SpFmo1 is required for echinochrome biosynthesis. Sulfotransferases are found from bacteria through higher eukaryotes. These enzymes catalyze the sulfate conjugation of several substrates resulting in either compound detoxification or bioactivation.

No description available.