The Aldo-Keto Reductases (AKR) are a group of oxidoreductase enzymes structurally and mechanistically distinct from the Alcohol Dehydrogenases (ADH). The AKRs are of importance for their ability to produce industrially useful compounds including chiral secondary alcohols. The ADH family have traditionally been exploited for chiral alcohol production; the AKR family have currently been underexploited for chiral alcohol production and present the opportunity to search for novel oxidoreductases with properties and substrate specificities distinct from the ADH enzymes. The AKR studied here, from the hyperthermophilic bacteria Thermotoga maritima has been characterised with respect to its biochemical and structural properties, and its potential as a biocatalyst evaluated. This enzyme is the second example of a thermophilic AKR to have its three dimensional structure solved, the other also being from Thermot. maritima. The AKR studied exhibits high stability with respect to temperature and moderate amounts of organic solvents. A large preference for the reduction reaction compared to the oxidation reaction was found, which has previously been observed in other AKRs. The X-ray crystal structure was solved to 2.6Å resolution in the apo form. The final structure has three loop sections which were not located due to disorder within the crystal, which are expected to become ordered upon cofactor and substrate binding. A section of one of these missing loops was found to bind at the active site of the enzyme, with a glutamate occupying the site of substrate carbonyl binding. The formation of a dimer, increased helix-dipole stabilisation and long distance ion pair interactions all act to increase thermostability of the AKR with respect to its mesophilic homologues. The X-ray crystal structure of Escherichia coli bacterioferritin has also been solved to 1.9Å resolution, which was co-purified along with the recombinant AKR enzyme. This structure shows the symmetrical binding of a heme molecule on the local two-fold axis between subunits and the binding of two metal atoms to each subunit at the ferroxidase centre. These metal atoms have been identified as zinc by the anaylsis of the structure and X-ray data and confirmed by microPIXE experiments. For the first time the heme has been shown to be linked to the internal and external environments via a cluster of waters positioned above the heme molecule. This information has provided a greater insight into the function and mechanism of bacterioferritin.

This is an investigation into alcohol dehydrogenases (ADHs) from Geobacillus thermoglucosidasius. Eighteen ADHs have been studied, with seven taken for closer inspection. Characterisation was carried out to determine the industrial significance of these enzymes, starting with the substrate scope of the ADHs. The key results obtained are as follows: ADH A is the alcohol dehydrogenase domain of the bifunctional ADHE enzyme (Extance, 2012; Extance et al., 2013). It has been determined that the substrate scope, whilst restricted to linear aliphatic aldehydes, extends at least to dodecanal. Also, with a specificity constant of 167 mM-1 min-1 it appears that ADH A could prefer butanal to shorter-chain aldehydes such as ethanal and propanal with specificity constants of 38 mM-1 min-1 and 35 mM-1 min-1, respectively. Thus ADH A may have a preference for longer aldehydes than previously believed due to its native role in the production of ethanol from acetyl-coA. ADH B was previously investigated for its potential role in the production of butanol. Here it was confirmed as an NADH-dependent ADH, with a substrate scope limited to five carbon length substrates and smaller, with residual activity with C6 substrates. ADH B demonstrated activity with ethyl 4-chloroacetoacetate, an intermediate in the production of statins. Further, an estimated half-life whilst stored at 4°C of 770 days; retention of 86% activity with 10vol% ethyl acetate and 92% activity with 10vol% acetonitrile; and a specific activity of 27 U mg-1 with 3M 2-butanone are all indications that ADH B is a potentially useful enzyme for industry. The last enzyme to be previously investigated was ADH C, which in this work was confirmed to be an acetoin reductase with a very small substrate scope exclusively based around the acetoin motif, and therefore no further work was conducted. ADH D and ADH F both have broad substrate scopes including the industrially-relevant substrates, 5-norbornene-2-carboxaldehyde, 1-phenyl-1,2-propanedione, ethyl 4-chloroacetoacetate and ethyl-2-oxo-4-phenylbutyrate. ADH D is an NADPH-dependent enzyme whereas ADH F can utilise both NADH and NADPH. Both enzymes are annotated as aldo-keto reductases, which is further indicated by multiple sequence alignment with the most similar available protein sequences and crystal structures. Thus, these two enzymes are the first aldo-keto reductases to be examined from moderate thermophiles, and are tentatively assigned in the AKR family as AKR6D1 and AKR5G4 respectively. ADH D has a very low KM (≤0.1 μM) with NADPH, giving a specificity constant of 2,800,000 mM-1 min-1, substantially higher than any other noted. ADH D showed >80% activity from pH 5.0 - 8.0. The enzyme was resistant to solvents DMSO (at 5 vol%) and ethyl acetate, acetonitrile and cyclopentyl methyl ether (at 20vol%). ADH F had the broadest substrate scope of any ADH tested, with 1-phenyl-1,2-propanedione the most preferred substrate with a KM of 0.010 mM and a specificity constant of 54,000 mM-1 min-1. It greatly preferred sodium phosphate at pH 7.0, as almost any deviation resulted in a substantial loss of activity. Activity of ≥70% was recorded in 5vol% DMSO, ethyl acetate, acetonitrile, cyclopentyl methyl ether and 50vol% hexane . Both ADH D and F have optimal activities at 70 °C and both may have application in the biotechnology industry for the production of pharmaceutical intermediates and other high value chemicals. ADH E acts solely as an aldehyde reductase, with Vmax using NADH of 74, 331, 320 and 281 U mg-1 for methanal, ethanal, propanal and butanal, respectively. Activity with NADPH was limited (< 1% compared with NADH). Activity was also noted with higher aldehydes such as octanal and furfural. ADH G is an NADPH-dependent ADH utilizing aldehydes only. It has an optimal temperature of 60°C with a half-life of under two hours at that temperature. In conclusion, this thesis reports a feasibility study into the potential industrial use of specific enzymes for a variety of purposes ranging from the production of pharmaceutical intermediates to bioremediation. ADHs D and F are most likely to have use in the biotechnology industry, and ADHs B and E may be suitable for cofactor regeneration. ADH E may additionally be useful in the bioremediation industry. In addition, the anticipated biological significance of these enzymes is described.

Endometriosis and breast cancer are sex hormone dependent diseases characterised by the local production of high levels of 17β-oestradiol. The relationship between prostaglandins and sex steroid hormones is one of the focal questions in endometriosis, breast cancer and other sex steroid hormone related disorders. Therefore, the main hypothesis was that the aldo-keto reductase (AKR) 1C isoenzymes are responsible for controlling the availability of 17β-oestradiol, progesterone and prostaglandins in the microenvironment of the endometrium, and surrounding adipose tissues of endometriotic lesions and breast tumours. This was investigated using quantitative real-time polymerase chain reaction (PCR) for measuring the gene expression of AKR1C1-3 enzymes, and prostaglandin E (1-4) and F receptors in the endometrium, and surrounding adipose tissues of endometriotic lesions and breast tumours. This was then followed by investigating the role of one of the AKR1C enzymes - AKR1C3 - by inhibiting its catalysis using bimatoprost, followed by using PGE2 as one of the main candidates acting as a transcription factor for upregulating the expression of AKR1C3 which in turn upregulates the production of the local 17β-oestradiol. The gene expression of AKR1C1 was significantly higher in endometriotic lesions compared to eutopic endometrium of endometriosis patients. However, there was no significant difference in the gene expression of AKR1C (1-3) enzymes in the surrounding adipose tissues of endometriotic lesions between patients with or without endometriosis. Also, there was no significant difference in the gene expression of AKR1C (1-3) enzymes in the breast adipose tissues of patients with breast tumours, regardless of the oestrogen or progesterone receptor status. The gene expression of prostaglandin E (EP) receptor subtype 3 was significantly higher in the endometriotic lesions compared to eutopic endometrium of endometriosis patients. In the omental adipose tissue, there was no significant difference in the gene expression of EP1-4 and FP receptors between endometriosis and non-endometriosis patients. In the breast adipose tissue, there was also no significant difference in the gene expression of EP1-4 and FP receptors in patients with breast cancer regardless of the oestrogen or progesterone receptor status. The inhibitory constant (Ki) of bimatoprost was determined using oestrone as a substrate: Ki = 2.9µM and αKi = 0.7µM. Bimatoprost also significantly inhibited the production of 17β-oestradiol and inhibited the production of 9α,11β PGF2 in a dose dependent manner in the human endometrial cells. The effect of PGE2 on the expression of AKR1C1 and AKR1C3 was assessed in the human endometrial cells. The EP4 receptor agonist, L-902688, increased the gene expression of AKR1C1 and AKR1C3. Despite gene expression elevation, L-902688 did not increase the production of 17β-oestradiol. In conclusion, the results were contradictory and highlighted the need for further investigation into the relationship between prostaglandins and sex steroid hormones in the microenvironment of the endometrium, and surrounding adipose tissues of endometriotic lesions and breast tumours.

Orientador: Anete Pereira de Souza / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-10T18:14:23Z (GMT). No. of bitstreams: 1 Rosselli_LucianaKauer_D.pdf: 3396544 bytes, checksum: 1ed6069e60d6f5966add93778319a1d0 (MD5) Previous issue date: 2007 / Resumo: o programa de seqüenciamento genômico da bactéria Xylella fastidiosa gerou um enorme número de ORFs ("Open Reading Frames" - quadro de leitura aberto ou genes putativos) pertencentes às categorias de patogenicidade, virulência e adaptação deste importante fitopatógeno. Uma destas ORFs (XF 1729) foi anotada como sendo uma fenilacetaldeído desidrogenase de 31,4 kDa. No entanto, a análise de sua seqüência primária de aminoácidos revelou similaridades com proteínas pertencentes à superfamília de aldo-ceto redutases. As proteínas desta superfamília são oxidorredutases NADPH-dependentes relacionadas funcionalmente e estruturalmente. Neste trabalho, a seqüência similar de X fastidiosa foi clonada no vetor de expressão pET32Xa/LIC com o objetivo de super expressar a proteína recombinante fusionada a seis resíduos de histidina em Escherichia colí BL21(DE3). A proteína expressa na fração solúvel foi purificada por cromatografia de afinidade em metal imobilizado (resina Agarose-IDA-Ni). O conteúdo de sua estrutura secundária foi verificado por espectroscopia de dicroísmo circular. As medidas de espalhamento de raios-X a baixo ângulo (SAXS) forneceram os parâmetros estruturais gerais (raio de giro de 27,5 :I: 0,8 Á e máxima dimensão de 90 Á) e indicaram que a proteína apresenta-se como um monômero em solução. Além disto, os cálculos estruturais ab initio mostraram que a proteína apresenta algumas similaridades com uma aldo-ceto redutase previamente cristalizada. A proteína XF 1729 purificada foi capaz de catalisar a redução dos substratos DL-gliceraldeído (Kcat 2.26 S-l, Km 8.20:1: 0.98 mM) e 2-nitrobenzaldeido (Kcat 11.74 S-l, Km 0.14:1: 0.04 mM) na presença de NADPH. A seqüência de aminoácidos da proteína XFI729 apresentou mais alta identidade (maior que 40%) com inúmeras proteínas de função desconhecida. Entre as AKRs identificadas, encontramos aproximadamente 29% dê identidade com YakC (AKRI3) de Schizosaccharomyces pombe, 30% e 28% com AKRIIA e AKRIIB, ambas de Baci/lus subtiZis, respectivamente. Os resultados estabeleceram a proteína XF 1729 como um novo membro da superfamília das AKRs, da nova sub-família AKR13B 1. Finalmente, os experimentos de caracterização por cromatografia de gel filtração indicaram que a proteína apresenta wna forma alongada, gerando wn peso molecular aparente maior que o esperado. Além da proteína AKRl3B 1, selecionamos mais duas proteínas codificadas pelas ORFs XFl934 e XFl532 para estudos de estrutura e função. A proteína HetI (XFI934), de 22,4 kDa, apresenta similaridade proteínas da família phosphopantetheinyl transferase, sendo necessária à síntese de ácido graxo via acetato na bactéria. A proteína XF1532, de 36,8 kDa, é sirpilar a reguladores transcricionais de extresse oxidativo, sendo sua seqüência similar (44%) à proteína OxyR de Escherichia coZi, a qual pertence à família LysR de reguladores transcricionais. As duas ORFs foram clonadas e expressas em Escherichia coZi, no entanto não foi possível obter a proteína na fração solúvel, impossibilitando o seguimento dos estudos de caracterização estrutural e funcional. A descrição da metodologia utilizada para produção destas proteínas e os resultados preliminares obtidos estão descritos no item Resultados Complementares desta tese. Um amplo benefício no conhecimento dos mecanismos de patogenicidade da X fastidiosa tem sido esperado, desde o seqüenciamento completo de seu genoma. Neste sentido, passos iniciais foram dados no sentido de se caracterizar a função das proteínas codificadas por seus genes / Abstract: The Xylella fastidiosa genome program generated a large number of gene sequences that belong to pathogenicity, virulence and adaptation categories from this important plant pathogen. One of these genes (XF 1729) was described in the genome annotation as being a phenylacetaldehyde dehydrogenase. However, the XF 1729 primary sequence analysis showed similarities to Aldo-keto reductase superfamily proteins. The AKRs are NADPH-dependent oxidoreductases structurally and functionally related. In this work, the similar sequence XF 1729 from Xylella fastidiosa was cloned onto the pET32Xa/LIC vector in order to over-express a recombinant His- Tag fusion protein in E. coli BL21(DE3). The expressed protein in the soluble fraction was purified 'by immobilized metal affinity chromatography (agarose-IDA-Ni resin). Secondary structure contents were verified by circular dichroism spectroscopy. Small-Angle X Ray Scattering (SAXS) measurements furnish general structural parameters (the particle radius of gyration of 27.5:J::0.8A and the particle maximum dimension of 90A) and provide a strong indication that the protein has a monomeric form in solution. Also, ab initio calculations show that the protein has some similarities with a previously crystallized aldo-keto reductase protein. The recombinant XF1729 purified to homogeneity catalyzed the reduction ofDL-glyceraldehyde (Kcat 2.26 S-I, Km 8.20:J:: 0.98 mM) and 2-nitrobenzaldehyde (Kcat 11.74 S-I, Km 0.14:J:: 0.04 mM) in the presence of NADPH The amino acid sequence deduced from XF 1729 showed the highest identity (40% or higher) with several functionally unknown proteins. Among the identified AKRs, we found approximately 29% of identity with YakC (AKR13) from Schizosaccharomyces pombe, 30% and 28% with AKR11A and AKR11B, both from Bacillus subtilis, respectively. The results establish XF 1729 as the new member of AKR family, AKR13B1. Finally, the first characterization by gel filtration chromatography assays indicates that the protein has an elongated shape, which generates an apparent higher rnolecular weight. Since Xylellafastidiosa 9a5c strain (associated with CVC) is the first plant pathogen to be fully sequenced, a large benefit for the whole field of disease research can be expected. An initial step has been taken towards the characterization the protein function encoded by its genes / Doutorado / Genetica de Microorganismos / Doutor em Genetica e Biologia Molecular

Das lineare Chromosom von S.lividans zeichnet sich durch eine hohe Variabilität insbesondere der chromosomalen Endbereiche aus. Hier finden sich unter anderen auch verschiedene Gene, die bisher einzigartig sind. Nach Klonierung der Gene in E.coli wurden die entsprechenden Genprodukte als His-Tag Fusionsproteine überproduziert, aufgereinigt und zur Herstellung von Antikörpern verwendet. Der untersuchte Abschnitt, als Ganzes und in Unterabschnitten, wurde auf einem Hoch Kopien Vektor in S.lividans transformiert. In extra hierfür konstruierten Vektorsystemen erfolgte die Produktion von His-Tag Proteinen in S.lividans. Nach Fusion von potentiellen Promoterbereichen mit dem promoterlosen EGFP-Gen, gelang deren Identifizierung in enhanced green fluorescent protein (EGFP) produzierenden S.lividans Transformanten. Mit Hilfe eines Vektors, der ein Temperatur sensitives Replikon besitzt, wurden Gene durch die Integration eines Hygromycin-Resistenzgenes ersetzt, bzw. als Fusionsgen mit dem EGFP-Gen erstellt. Ein Flavoprotein wurde zur Homogenität gereinigt. Es wurde nachgewiesen, dass in S.lividans pro Monomer ein FAD-Molekül interagiert. Physiologische Studien zeigen, dass die Synthese des chromosomal determinierten Proteins in S.lividans nur erfolgt, wenn dieser Stamm ein Plasmid- oder chromosomal- kodiertes Thiostrepton Resistenzprotein (23S rRNA Methylase) enthält. Es muss geschlussfolgert werden, dass die Methylierung der 23S rRNA die Translation verschiedener mRNAs beeinflusst. Die Synthese dieses Proteins ist des Weiteren abhängig von hohen Konzentrationen an NaCl und KCl im Medium, wie auch die zweier Aldo-Keto Reduktasen. Disruptionsmutanten eines dieser zwei Aldo-Keto Reduktase-Gene zeigen jeweils eine erhöhte und verfrühte Produktion eines rot gefärbten Mycel-assoziierten Antibiotikums (Undecylprodigiosin), während die eines weiteren (Actinorhodin) unbeeinflusst blieb.

Prostate cancer is the most commonly diagnosed non-skin cancer in men and the second leading cause of cancer death in the United States. Prostate cancer, like many cancers, is a disease that generally requires a long period of time to develop and grow before it becomes detectable. This long period of latency makes prostate cancer a candidate for dietary chemoprevention. Soy and selenium (Se), are associated with a decreased risk of prostate cancer. We previously showed that high dietary intake of selenium (Se) and soy isoflavones decreased the expression of the androgen receptor (AR) and AR-regulated genes in the prostates of healthy rats. In this study we hypothesized that the downregulation of AR and AR-regulated genes would inhibit tumorigenesis in the transgenic adenocarcinoma of the mouse prostate (TRAMP) mouse. Mice were fed one of two stock diets with or without a supplement of Se in a 2 X 2 factorial design. The stock diets provided high or low dietary isoflavones. Mice were exposed to the diets from conception and sacrificed at 18 or 24 weeks of age. Prostate histopathology, urogenital tract (UGT) weight, serum IGF-1 levels, and the expression of AR and AR-regulated genes in the dorsolateral prostate was examined using quantitative PCR and Western blotting. Urogenital tract (UGT) weight was reduced compared to control in all dietary groups containing high Se, isoflavones, or both at 24 weeks (p<0.005). Dietary isoflavones delayed tumor progression and downregulated protein levels of AR, AR-regulated genes, and upregulated the protective FOXO1 and FOXO3a transcription factors. High dietary isoflavones also decreased the phosphorylation of the IGF-1R. The only main effect of Se was the upregulation of AKR1C14 the enzyme that deactivates 5&aplha;-DHT.This study identifies a previously unknown effect of isoflavones in the upregulation of FOXO expression and confirms previous studies of isoflavones' anticancer effects. Further research is needed to find a protective dose or form of Se and to elucidate the mechanism of isoflavones.

Yes / The aldo-keto reductase 1C3 isoform (AKR1C3) plays a vital role in the biosynthesis of androgens, making this enzyme an attractive target for castration-resistant prostate cancer therapy. Although AKR1C3 is a promising drug target, no AKR1C3-targeted agent has to date been approved for clinical use. Flufenamic acid, a non-steroidal anti-inflammatory drug, is known to potently inhibit AKR1C3 in a non-selective manner as COX off-target effects are also observed. To diminish off-target effects, we have applied a scaffold hopping strategy replacing the benzoic acid moiety of flufenamic acid with an acidic hydroxyazolecarbonylic scaffold. In particular, differently N-substituted hydroxylated triazoles were designed to simultaneously interact with both subpockets 1 and 2 in the active site of AKR1C3, larger for AKR1C3 than other AKR1Cs isoforms. Through computational design and iterative rounds of synthesis and biological evaluation, novel compounds are reported, sharing high selectivity (up to 230-fold) for AKR1C3 over 1C2 isoform and minimal COX1 and COX2 off-target inhibition. A docking study of compound 8, the most interesting compound of the series, suggested that its methoxybenzyl substitution has the ability to fit inside subpocket 2, being involved in π-π staking interaction with Trp227 (partial overlapping) and in a T-shape π-π staking with Trp86. This compound was also shown to diminish testosterone production in the AKR1C3-expressing 22RV1 prostate cancer cell line while synergistic effect was observed when 8 was administered in combination with abiraterone or enzalutamide. / University of Turin (Ricerca Locale grant 2014 and 2015) and Prostate Cancer UK grant S12-027

Yes / The aldo-keto reductase 1C3 (AKR1C3) enzyme is considered an attractive target in Castration Resistant Prostate Cancer (CRPC) because of its role in the biosynthesis of androgens. Flufenamic acid, a non-selective AKR1C3 inhibitor, has previously been subjected to bioisosteric modulation to give rise to a series of compounds with the hydroxytriazole core. In this work, the hit compound of the previous series has been modulated further, and new, more potent, and selective derivatives have been obtained. The poor solubility of the most active compound (cpd 5) has been improved by substituting the triazole core with an isoxazole heteronucleous, with similar enzymatic activity being retained. Potent AKR1C3 inhibition is translated into antiproliferative effects against the 22RV1 CRPC cellular model, and the in-silico design, synthesis and biological activity of new compounds is described herein. Compounds have also been assayed in combination with two approved antitumor drugs, abiraterone and enzalutamide. / This research was financially supported by the University of Turin (Ricerca Locale grants BOSD_RILO_20_01, LOLM_RILO_21_01, PIPA_RILO_20_01 and PIPA_RILO_21_01), Fondazione Cassa di Risparmio di Torino (Grant BOSD_CRT_17_2) and TUBITAK (The Scientific and Technological Research Council of Turkey-2219 program).

Yes / The aldo-keto reductase 1C3 (AKR1C3) isoform plays a vital role in the biosynthesis of androgens and is considered an attractive target in prostate cancer (PCa). No AKR1C3-targeted agent has to date been approved for clinical use. Flufenamic acid and indomethacine are non-steroidal anti-inflammatory drugs known to inhibit AKR1C3 in a non-selective manner as COX off-target effects are also observed. Recently, we employed a scaffold hopping approach to design a new class of potent and selective AKR1C3 inhibitors based on a N-substituted hydroxylated triazole pharmacophore. Following a similar strategy, we designed a new series focused around an acidic hydroxybenzoisoxazole moiety, which was rationalised to mimic the benzoic acid role in the flufenamic scaffold. Through iterative rounds of drug design, synthesis and biological evaluation, several compounds were discovered to target AKR1C3 in a selective manner. The most promising compound of series (6) was found to be highly selective (up to 450-fold) for AKR1C3 over the 1C2 isoform with minimal COX1 and COX2 off-target effects. Other inhibitors were obtained modulating the best example of hydroxylated triazoles we previously presented. In cell-based assays, the most promising compounds of both series reduced the cell proliferation, prostate specific antigen (PSA) and testosterone production in AKR1C3-expressing 22RV1 prostate cancer cells and showed synergistic effect when assayed in combination with abiraterone and enzalutamide. Structure determination of AKR1C3 co-crystallized with one representative compound from each of the two series clearly identified both compounds in the androstenedione binding site, hence supporting the biochemical data. / University of Turin (Ricerca Locale grant 2015-2017) and Prostate Cancer UK grant S12-027.

<p>Истраживање има фокус на хуманим ензимима из суперфамилије алдо-кето редуктаза, које имају велики метаболички значај за хомеостатско функционисање организма. Неки од чланова подфамилије 1С алдо-кето редуктаза (AKR1C) имају улогу у развоју одређених патолошких стања, као што су леукемија, тумори простате,<br />дојке и ендометријума, као и у смањивању ефекта хемотерапија. До сада није регистрован лек који директно утиче на протеине ове групе и самим тим је акценат на изналажењу специфичних лиганада (супстрата, инхибитора), који би могли да имају фармаколошку примену, али и на утврђивању везе између структуре и функције испитиваних лиганада према ензиму. Теза је имала фокус на протеину<br />AKR1C3. У овој дисертацији је представљена оптимизација ензимског есеја и испитивање потенцијалних лиганада и њиховог ефекта на ензимску активност одређених хуманих изоформи протеина из подфамилије AKR1C. Тестирана су синтетисанa стероиднa jeдињења, комерцијална једињења и биљни екстракти. Стероидни лиганди (<strong>AKR-1, -2, -3, -7, -9, -19</strong> и <strong>-22</strong>) који су показали добре инхибиторне карактеристике су детаљније описани одређеним добијеним<br />кинетичким параметрима и затим су кокристализовани са протеином и<br />кофакторм. Од 7 различитих комплекса протеина са најбољиминхибитором, за два комплекса су добијене дифракције са инхибитором и решене кристалне структуре са лигандом у везном месту и врло добром резолуцијом, <strong>AKR-7: 1.7 &Aring;, AKR -19: 1.6 &Aring;.</strong> Ови резултати представљају прве протеинске кристале чију су структуру решили истраживачи из Србије, а у научном смислу и одличну основу за даљи дизајн и тестирање једињења и кокристализације.</p> / <p>Istraživanje ima fokus na humanim enzimima iz superfamilije aldo-keto reduktaza, koje imaju veliki metabolički značaj za homeostatsko funkcionisanje organizma. Neki od članova podfamilije 1S aldo-keto reduktaza (AKR1C) imaju ulogu u razvoju određenih patoloških stanja, kao što su leukemija, tumori prostate,<br />dojke i endometrijuma, kao i u smanjivanju efekta hemoterapija. Do sada nije registrovan lek koji direktno utiče na proteine ove grupe i samim tim je akcenat na iznalaženju specifičnih liganada (supstrata, inhibitora), koji bi mogli da imaju farmakološku primenu, ali i na utvrđivanju veze između strukture i funkcije ispitivanih liganada prema enzimu. Teza je imala fokus na proteinu<br />AKR1C3. U ovoj disertaciji je predstavljena optimizacija enzimskog eseja i ispitivanje potencijalnih liganada i njihovog efekta na enzimsku aktivnost određenih humanih izoformi proteina iz podfamilije AKR1C. Testirana su sintetisana steroidna jedinjenja, komercijalna jedinjenja i biljni ekstrakti. Steroidni ligandi (<strong>AKR-1, -2, -3, -7, -9, -19</strong> i <strong>-22</strong>) koji su pokazali dobre inhibitorne karakteristike su detaljnije opisani određenim dobijenim<br />kinetičkim parametrima i zatim su kokristalizovani sa proteinom i<br />kofaktorm. Od 7 različitih kompleksa proteina sa najboljiminhibitorom, za dva kompleksa su dobijene difrakcije sa inhibitorom i rešene kristalne strukture sa ligandom u veznom mestu i vrlo dobrom rezolucijom, <strong>AKR-7: 1.7 &Aring;, AKR -19: 1.6 &Aring;.</strong> Ovi rezultati predstavljaju prve proteinske kristale čiju su strukturu rešili istraživači iz Srbije, a u naučnom smislu i odličnu osnovu za dalji dizajn i testiranje jedinjenja i kokristalizacije.</p> / <p>This research focuses on human enzymes of the aldo-keto reductase superfamily, whose functions have a significant metabolic impact on organism homeostasis. Some members of the 1C aldo-keto reductase (AKR1C) subfamily play role in the development of specific pathological conditions, such as leukaemia, prostate cancer, breast cancer and endometrial cancer, as well as reducing the effectivness of chemotherapy. However, currently there are no approved and registered drugs that directly affect proteins from this subfamily. Therefore our main aim was to screen for specific ligands (substrates, inhibitors) with potential pharmacological applications, and to establish structure-activity relationships for these ligands and enzymes. This thesis mainly focuses on isoform AKR1C3. In this dissertation, optimization of an enzymatic assay and testing of potential&nbsp; ligands and their effects on the enzymatic<br />activity of specific human isoforms of proteins from subfamily AKR1C are presented. Tested ligands include synthetic steroidal compounds, commercial compounds and plant extracts. Steroid compounds, <strong>AKR-1, -2, -3, -7, -9, -19</strong> and -<strong>22</strong>, were found to be&nbsp;&nbsp; good inhibitors of AKR1C3, and further kinetic studies were conducted. Finally, cocrystalization of protein AKR1C3 with cofactor and these inhibitors was accomplished. From 7 different complexes of protein with inhibitors, two structures were solved to very high resolution, <strong>AKR-7: 1.7 &Aring;, AKR -19: 1.6 &Aring;</strong>. These results represent the first protein crystal structures solved by researchers from Serbia, and&nbsp; results provide an excellent basis for further design and testing of new inhibitors.</p>