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PubMed1980

In vitro steroidogenesis in testes of three infants, two with ambiguous external genitalia and one with true precocious puberty: Evidence for the presence of active 17 beta-hydroxysteroid oxidoreductase in immature human testes.

The present report investigated steroidogenesis in vitro in testis tissues obtained from two boys aged 8 months and 4 years with ambiguous external genitalia and male vagina, and a 4-year-old body with true precocious puberty. Histologically, testes of the former two boys are still immature and the testis of the last one contains differentiated Sertoli cells and primary spermatocytes, but no mature Leydig cells are recognized in any of them. In each testis, 17 beta-hydroxysteroid oxidoreductase is active for androstenedione in the presence of an excess amount of NADPH, while delta 5-3 beta-hydroxysteroid dehydrogenase and delta 4-steroid 5 alpha-reductase activities are limited. 17 alpha-Hydroxylase and C17--20 lyase are significantly active in each testis and are enhanced in the testis of the boy with precocious puberty. Although the testis tissue used in the present study may not be biologically normal and the number of cases investigated is still limited, the above results indicate that active 17 beta-hydroxysteroid oxidoreductase is present in immature human testes and that delta 5-3 beta-hydroxysteroid dehydrogenase may become active in the human testis at the advanced stage of the development of testicular function during the puberty.

17-Hydroxysteroid Dehydrogenases↗
PubMed2005

Novel processing and localization of catA, ccdA associated thiol-disulfide oxidoreductase, in protein hyper-producing bacterium Brevibacillus choshinensis.

Previously, we have cloned ccdA and its associated thiol-disulfide oxidoreductase gene, catA, in Brevibacillus choshinensis. CcdA is known to be an integral membrane protein and its associated oxidoreductase homologues are believed to be membrane anchoring proteins, both providing reducing equivalents across the membrane to control correct disulfide bond formation. Here, we found that CatA is first localized as a membrane bound form and then slowly released into the cellular periphery and culture medium with cleavage at a novel processing site.

Amino Acid Sequence↗
PubMed2004

The ability of new sugar-modified derivatives of antitumor anthracycline, daunorubicin, to stimulate NAD(P)H oxidation in different cellular oxidoreductase systems: NADH dehydrogenase, NADPH cytochrome P450 reductase, and xanthine oxidase.

Numerous data indicate that cellular oxidoreductases may be responsible for the cardiotoxic effects of antitumor anthracycline drugs as a consequence of the mediation by these agents of one-electron transfer from reduced nucleotides to atmospheric oxygen. This process is catalyzed primarily by NADH dehydrogenase, NADPH cytochrome P450 reductase, and xanthine oxidase and leads to the formation of reactive oxygen species (ROS). In this work the data on the ability of new amino sugar derivatives of daunorubicin to stimulate NAD(P)H oxidation in the above oxidoreductase systems are presented. They represent analogues of daunorubicin in which the amino sugar nitrogen is bounded to an unsubsituted, or amino- or nitro-substituted benzyl group. It was found that the ability of examined sugar-modified derivatives of daunorubicin to stimulate NAD(P)H oxidation differs considerably depending on the subsituent in the phenyl ring. It was also determined that this ability was not identical in the three enzymatic systems studied, showing that these derivatives have different affinities for the enzymes examined. More similarities were observed in their interaction with NADH dehydrogenase and NADPH cytochrome P450 reductase than with xanthine oxidase.

Antibiotics, Antineoplastic↗
PubMed2006

Purifications and characterizations of a ferredoxin and its related 2-oxoacid:ferredoxin oxidoreductase from the hyperthermophilic archaeon, Sulfolobus solfataricus P1.

The coenzyme A-acylating 2-oxoacid:ferredoxin oxidoreductase and ferredoxin (an effective electron acceptor) were purified from the hyperthermophilic archaeon, Sulfolobus solfataricus P1 (DSM1616). The purified ferredoxin is a monomeric protein with an apparent molecular mass of approximately 11 kDa by SDS-PAGE and of 11,180+/-50 Da by MALDI-TOF mass spectrometry. Ferredoxin was identified to be a dicluster, [3Fe-4S][4Fe-4S], type ferredoxin by spectrophotometric and EPR studies, and appeared to be zinc-containing based on the shared homology of its N-terminal sequence with those of known zinc-containing ferredoxins. On the other hand, the purified 2-oxoacid: ferredoxin oxidoreductase was found to be a heterodimeric enzyme consisting of 69 kDa alpha and 34 kDa beta subunits by SDS-PAGE and MALDI-TOF mass spectrometry. The purified enzyme showed a specific activity of 52.6 units/mg for the reduction of cytochrome c with 2-oxoglutarate as substrate at 55 degrees C, pH 7.0. Maximum activity was observed at 70 degrees C and the optimum pH for enzymatic activity was 7.0 -8.0. The enzyme displays broad substrate specificity toward 2-oxoacids, such as pyruvate, 2-oxobutyrate, and 2-oxoglutarate. Among the 2-oxoacids tested (pyruvate, 2-oxobutyrate, and 2-oxoglutarate), 2-oxoglutarate was found to be the best substrate with Km and kcat values of 163 microM and 452 min(-1), respectively. These results provide useful information for structural studies on these two proteins and for studies on the mechanism of electron transfer between the two.

Amino Acid Sequence↗
PubMed1999

Cellular expression of xanthine oxidoreductase protein in normal human tissues.

Xanthine oxidoreductase is an important cytoplasmic source of reactive oxygen species, and has been implicated in the pathogenesis of ischemia-reperfusion damage. Because the cellular localization of this protein remains unclear, our aim was to study its distribution in fresh normal human tissue obtained at surgery. For immunohistochemical studies we purified the protein from human milk and raised a polyclonal antibody in rabbits. In the liver the protein was preferentially localized to the periportal hepatocytes and it was absent from the perivenous region. In the proximal intestine, the protein was expressed in epithelial cells and goblet cells. Lactating mammary gland acinar cells showed intense staining. Small vessel vascular endothelial cells of the intestine, mammary gland, and skeletal muscle showed immunoreactivity, but in the kidney, glomerular endothelial cells were negative. No cells in the heart, brain, or lung expressed the enzyme protein. The observed localization of the xanthine oxidoreductase protein is consistent with previously observed enzyme activities in the organs studied. The widely assumed exclusive localization to capillary endothelium obviously does not apply to humans.

Animals↗
PubMed2000

Chemoprevention of aflatoxin B1 hepatocarcinogenesis by coumarin, a natural benzopyrone that is a potent inducer of aflatoxin B1-aldehyde reductase, the glutathione S-transferase A5 and P1 subunits, and NAD(P)H:quinone oxidoreductase in rat liver.

Structurally diverse compounds can confer resistance to aflatoxin B1 (AFB1) hepatocarcinogenesis in the rat. Treatment with either phytochemicals [benzyl isothiocyanate, coumarin (CMRN), or indole-3-carbinol] or synthetic antioxidants and other drugs (butylated hydroxyanisole, diethyl maleate, ethoxyquin, beta-naphthoflavone, oltipraz, phenobarbital, or trans-stilbene oxide) has been found to increase hepatic aldo-keto reductase activity toward AFB1-dialdehyde and glutathione S-transferase (GST) activity toward AFB1-8,9-epoxide in both male and female rats. Under the conditions used, the natural benzopyrone CMRN was a major inducer of the AFB1 aldehyde reductase (AFAR) and the aflatoxin-conjugating class-alpha GST A5 subunit in rat liver, causing elevations of between 25- and 35-fold in hepatic levels of these proteins. Induction was not limited to AFAR and GSTA5: treatment with CMRN caused similar increases in the amount of the class-pi GST P1 subunit and NAD(P)H: quinone oxidoreductase in rat liver. Immunohistochemistry demonstrated that the overexpression of AFAR, GSTA5, GSTP1, and NAD(P)H:quinone oxidoreductase affected by CMRN is restricted to the centrilobular (periacinar) zone of the lobule, sometimes extending almost as far as the portal tract. This pattern of induction was also observed with ethoxyquin, oltipraz, and trans-stilbene oxide. By contrast, induction of these proteins by beta-naphthoflavone and diethyl maleate was predominantly periportal. Northern blotting showed that induction of these phase II drug-metabolizing enzymes by CMRN was accompanied by similar increases in the levels of their mRNAs. To assess the biological significance of enzyme induction by dietary CMRN, two intervention studies were performed in which the ability of the benzopyrone to inhibit either AFB1-initiated preneoplastic nodules (at 13 weeks) or AFB1-initiated liver tumors (at 50 weeks) was investigated. Animals pretreated with CMRN for 2 weeks prior to administration of AFB1, and with continued treatment during exposure to the carcinogen for a further 11 weeks, were protected completely from development of hepatic preneoplastic lesions by 13 weeks. In the longer-term dietary intervention, treatment with CMRN before and during exposure to AFB1 for a total of 24 weeks was found to significantly inhibit the number and size of tumors that subsequently developed by 50 weeks. These data suggest that consumption of a CMRN-containing diet provides substantial protection against the initiation of AFB1 hepatocarcinogenesis in the rat.

Aflatoxin B1↗
PubMedDate not supplied

[Effect of platinum derivatives on microsomal NADPH-oxidoreductase activity].

The influence of platinum derivatives, cisplatin (cis-diamminedichloroplatinum) and imidazolplatin (cis-diimidazoledichloroplatinum) on the activity of rat liver microsomal NADPH-oxidoreductases was investigated in vitro using spectrophotometrical and chemiluminometrical methods. In the range of concentrations from 1 to 12 microM cisplatin inhibited NADPH-cytochrome c-reductase activity and NADPH/lucigenin-dependent chemiluminescence of microsomes. The 3 microM cisplatin decreased the NADPH-dependent reductase activity by 50%. At concentrations less than 2.5 mM sanazole (drug AK-2123) did not prevent the inhibiting influence of cisplatin on microsomal NADPH-dependent reductases. Imidazolplatin insignificantly inhibited NADPH-reductases. It is concluded that negligible inhibiting effect of imidazolplatin on microsomal NADPH-oxidoreductase allows us to consider this platinum derivative as a promising compound for further experimental trials as anticancer drug with low toxic action on the normal tissues of an organism.

Animals↗
PubMed2002

Glutathione S-transferase P1 and NADPH quinone oxidoreductase polymorphisms are associated with aberrant promoter methylation of P16(INK4a) and O(6)-methylguanine-DNA methyltransferase in sputum.

Inactivation of the p16(INK4a) tumor suppressor gene and O(6)-methylguanine-DNA methyltransferase (MGMT) DNA repair gene by aberrant promoter methylation appears to be an important step in respiratory carcinogenesis after exposure to tobacco smoke and radon progeny. The determinants of aberrant promoter methylation are not well characterized. Polymorphic variants of genes of which the products are involved in pathways that modulate and repair DNA damage after carcinogen exposure may affect the occurrence of de novo promoter methylation. On the basis of their associations with risk of lung cancer, we hypothesized that functional polymorphic variants of the NADPH quinone oxidoreductase, glutathione S-transferases P1 and M1, myeloperoxidase, and XRCC1 genes are associated with p16 and/or MGMT promoter methylation in sputum from cancer-free subjects at high risk for developing lung cancer. This hypothesis was tested by conducting a cross-sectional study of 70 former uranium miners from the Uranium Epidemiological Study cohort who were at high risk for lung cancer. The polymorphic variant genotypes were characterized through PCR-RFLP on DNA isolated from peripheral lymphocytes, and the methylation status of the p16 and MGMT promoters was determined by methylation-specific PCR on DNA isolated from sputum. Subjects who had at least one GSTP1 polymorphic allele (A-to-G at bp 104) had an increased risk for MGMT methylation [odds ratio (OR), 4.8; 95% confidence interval (CI), 1.2-18.6] or for either p16 or MGMT methylation (OR, 4.4; 95% CI, 1.3-14.2). Lack of a wild-type NADPH quinone oxidoreductase allele (C at bp 609) was also associated with methylation of either p16 or MGMT (OR, 3.1; 95% CI, 1.0-9.2). These results provide the first link between germ-line functional deficits in pathways that protect the cell from tobacco- and radon-induced DNA damage, and the development of aberrant promoter methylation of the p16 and MGMT genes in the respiratory epithelium of individuals at high risk for lung cancer.

Cyclin-Dependent Kinase Inhibitor p16↗
PubMed1990

Inhibition of rat liver NAD(P)H:quinone acceptor oxidoreductase (DT-diaphorase) by flavonoids isolated from the Chinese herb scutellariae radix (Huang Qin).

The glucuronide conjugates of oroxylin A and two other flavones, baicalein, and wogonin, were isolated from the methanol extract of the herb scutellariae radix (Huang Qin) and were found to be inhibitors of rat liver NAD(P)H:quinone acceptor oxidoreductase (EC 1.6.99.2). Baicalin (baicalein 7-O-glucuronide) and oroxylin-A 7-O-glucuronide are approximately 50-fold more potent than wogonin 7-O-glucuronide. The enzyme kinetic analysis revealed that oroxylin-A 7-O-glucuronide is a competitive inhibitor with respect to NADH (the electron donor), with a Ki value of 63 nM. Considering the similarities of their structures and inhibition kinetics to those of dicoumarol, it is thought that oroxylin-A 7-O-glucuronide and the other two flavonoids bind to an identical site and inhibit this quinone reductase in the same fashion as dicoumarol. The results also suggest that the inhibition of NAD(P)H:quinone acceptor oxidoreductase or another vitamin K reductase by oroxylin-A 7-O-glucuronide and the related flavonoids may be one of the steps associated with the anticoagulation action of the herb. These compounds are potentially useful anticoagulant drugs.

Animals↗
PubMed1991

Molecular characterization of the gor gene encoding glutathione reductase from Pseudomonas aeruginosa: determinants of substrate specificity among pyridine nucleotide-disulphide oxidoreductases.

In order to investigate the basis of functional diversity among the pyridine nucleotide-oxidoreductases the gor gene from Pseudomonas aeruginosa PAO, which encodes glutathione reductase, was analysed. The P. aeruginosa gor gene was identified by hybridization with a short DNA sequence from the gene encoding mercuric reductase in transposon Tn501. The gene was cloned, sequenced and overexpressed in Escherichia coli. Expression of the gene enabled rescue of an E. coli gor- mutant, confirming the identity of the cloned gene. The predicted sequence of the gene product showed homology with other members of the pyridine nucleotide-disulphide oxidoreductase family, and allowed determination of positions that may be involved in substrate specificity. These predictions provided information on the relationship of sequence to function, independently of structural data used in previous studies.

Amino Acid Sequence↗
PubMed1978

Purification and properties of a nucleoside diphosphosugar: NAD+ 2-hexosyl oxidoreductase.

Penicillium charlesii contains a nucleoside diphosphosugar: NAD 2-hexosyl oxidoreductase that oxidizes UDPgalactose (UDP-Galp), ADPribose [1,2] and UDPglucose (UDP-Glc). Dithiothreitol, NAD and 0.25 M NaCl but not nucleoside diphosphates stabilize the enzyme activity. The enzyme was purified and separated on polyacrylamide disc gels by electrophoresis into one major and eight minor bands of protein. Oxidoreductase activity was located in the major and three of the minor bands of protein. Each of these proteins catalyze the oxidation of UDPGalp, ADPribose and UDP-Glc.

Carbohydrate Dehydrogenases↗
PubMed1990

Isolation and characterization of the alkane-inducible NADPH-cytochrome P-450 oxidoreductase gene from Candida tropicalis. Identification of invariant residues within similar amino acid sequences of divergent flavoproteins.

The gene coding for the Candida tropicalis NADPH-cytochrome P-450 oxidoreductase (CPR, NADPH: ferricytochrome oxidoreductase, EC 1.6.2.4) was isolated by immunoscreening of a C. tropicalis lambda gt11 expression library and colony hybridization of a C. tropicalis genomic library. The C. tropicalis CPR gene produces a 2.35-kilobase mRNA transcript, levels of which were shown to be increased 16-fold in cells grown on tetradecane relative to cells grown on glucose as the sole carbon source. A 3-kilobase DNA fragment was sequenced, including 554 and 397 base pairs of 5'- and 3'-noncoding sequence, respectively. A single open reading frame of 2040 base pairs was identified and predicts a 76,683-Da polypeptide of 680 amino acid residues. The deduced C. tropicalis CPR amino acid sequence was compared with each of the CPR sequences reported from other organisms and invariant residues were identified. Multiple pairwise alignments of divergent members of protein families, previously recognized for their sequence similarities in their respective binding domains for FMN, FAD, and NADPH, have allowed identification of a subset of these invariant residues. From these analyses we infer the importance of 25 of the 680 amino acid residues.

Alkanes↗
PubMed1990

Studies on the NADH-menaquinone oxidoreductase segment of the respiratory chain in Thermus thermophilus HB-8.

Five distinct low potential iron-sulfur clusters have been identified potentiometrically in the membrane particles from Thermus thermophilus HB-8. Three of these clusters (designated as [N-1H]T, [N-2H]T, and [N-3]T) exhibit the following midpoint redox potentials and g values (Em8.0 = -274 mV, gx,y,z = 1.93, 1.94, 2.02), (Em8.0 = -304 mV, gx,y,z = 1.89, 1.95, 2.04), and (Em8.0 = -289 mV, gx,y,z = 1.80, 1.83, 2.06), respectively. These clusters, one binuclear and two tetranuclear, have been shown to be components of the energy coupled NADH-menaquinone oxidoreductase complex (NADH dh I). They are reducible by NADH in the piericidin A-inhibited aerobic membrane particles as well as in the purified NADH dh I complex. Two additional very low potential iron-sulfur clusters (one binuclear, [N-1L]T, and one tetranuclear, [N-2L]T) were observed in membrane particles. These clusters possess the following physiochemical properties (Em8.0 = -418 mV, gx,y,z = 1.93, 19.5, 2.02) and (Em8.0 = -437 mV, gx,y,z = 1.89, 1.95, 2.04), respectively. No high potential tetranuclear cluster equivalent to the mitochondrial iron-sulfur cluster [N-2]B was found in this bacterial system. In membrane particles isolated from T. thermophilus HB-8 cells, four different semiquinone species have been identified based on their redox midpoint potentials [Em9(Q/QH2) = 40, -100, -160, -300 mV] and sensitivity to the quinone analogue inhibitor, 2-heptyl-4-hydroxy quinoline-N-oxide. Of these semiquinone species the -100 mV component has been suggested to be part of the NADH dehydrogenase. Piericidin A sensitive delta psi formation has been demonstrated to be coupled to the NADH-MQ1 oxidoreductase in membrane vesicles of T. thermophilus HB-8.

Cell Membrane↗
PubMed1975

Properties of delta5-3beta-hydroxysteroid oxidoreductase isolated from Streptomyces griseocarneus.

Delta5-3beta-hydroxysteroid oxidoreductase was extracted in magnesium-containing Tris buffer from sonicated Streptomyces griseocarneus cells. The enzyme was partially purified (150 X) by ion exchange chromatography and gel filtration following (NH4)2SO4 fractionation. Upon gel filtration on Sephadex G-75 to G-200, the greatest part of the activity gave a peak in the fractionation range. The enzyme obtained from the gel yielded small enzyme molecules on repeated chromatography. A molecular weight of 32 to 36 000 was calculated for the activity appearing in the fractionation range of Sephadex G-75 to G-200. The enzyme is highly specific for the irreversible oxidation of the 3beta-hydroxyl group in steroids with a trans-anellated A : B ring system with either C5 or C6 double bond. Delta5-3-ketosteroids are converted into delta5-3-ketosteroids at a high rate, but the isomerase activity cannot be separated from the oxidoreductase activity either by chromatography or by selective heat inactivation. NAD, NADP, FMN or FAD did not influence the activity, but the enzyme is inactive in the absence of molecular oxygen.

Androstenedione↗
PubMedDate not supplied

[Thyroid hormones and mitochondrial cytochrome c oxidoreductase activity].

In the experiments on albino male rats it was shown that thyroid hormones, exerting organospecific effect, control both the activity and the amount of cytochrome-c-oxidoreductase in hepatic, renal, cardiac and cerebral mitochondria. In the mechanism of cytochrome-c-oxidoreductase regulation thyroxin effect is likely to be mediated by cytochrome c amount. Supraphysiological thyroxin concentrations exert a direct action on the enzyme, whereas its physiological levels regulate cytochrome-c-oxidase, acting as an inductor.

Animals↗
PubMed1994

Diphenyleneiodonium inhibits reduction of iron-sulfur clusters in the mitochondrial NADH-ubiquinone oxidoreductase (Complex I).

Diphenyleneiodonium (DPI) inhibits the mitochondrial NADH-ubiquinone oxidoreductase (Complex I) on the substrate side of the Fe-S clusters. In the inhibited NADH-supplemented state all of the Fe-S clusters are oxidized, whereas the reduced minus oxidized difference spectrum of the protein-bound FMN can be visualized. It is characterized by troughs at 370 and 450 nm and a small increase of absorbance in the 500-700-nm region. DPI probably reacts irreversibly with FMN, because oxidation of FMN is blocked even after its extraction from the enzyme. Inhibition requires preincubation of enzyme in the presence of NADH and DPI. The lower the NADH/NAD+ ratio or the pH, or the higher the NAD+/DPI ratio, the more DPI is required for inhibition. NAD+ and DPI apparently compete for a common site. Both ubiquinone and dichlorophenolindophenol reductase activities are fully blocked by DPI, whereas the ferricyanide reductase activity is inhibited by 75%. Similar results were found with Complex I and two rotenone-insensitive preparations, subcomplex I lambda and the flavoprotein fraction. DPI also inhibits NADH oxidation by bacterial NADH-ubiquinone oxidoreductase-1 (NDH-1) in membranes of Paracoccus denitrificans and Escherichia coli.

Electron Spin Resonance Spectroscopy↗
PubMed1994

Metal-catalyzed oxidation of Fe2+ dehydrogenases. Consensus target sequence between propanediol oxidoreductase of Escherichia coli and alcohol dehydrogenase II of Zymomonas mobilis.

We have studied two enzymes of a newly described family of dehydrogenases with high sequence homology, 1,2-propanediol oxidoreductase of Escherichia coli and alcohol dehydrogenase II of Zymomonas mobilis. These enzymes perform their metabolic role under anaerobic conditions; in the presence of oxygen, they show a very similar inactivation pattern by a metal-catalyzed oxidation system. Titration of histidine residues with diethyl pyrocarbonate showed one histidine residue less in the oxidized enzymes. Comparison of subtilisin peptide maps of active and inactivated enzymes showed a difference in one histidine-containing peptide, the sequence of which is YNTPH277GVAN for propanediol oxidoreductase and YNLPH277GV for alcohol dehydrogenase II. This histidine residue lies 10 residues away from a proposed metal-binding site, H263XXXH267, necessary to explain a site-specific free radical mechanism. The three histidine residues here described are strictly conserved in all enzymes of this family. In this report we propose that histidine 277 is a target for oxidation by a metal-catalyzed oxidation system and that this modification leads to the irreversible inactivation of both enzymes.

Alcohol Dehydrogenase↗
PubMed1990

Characterization of the purified pituitary cytosolic NADPH:5 alpha-dihydroprogesterone 3 alpha-hydroxysteroid oxidoreductase.

The purified cytosolic 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR) from female rat pituitary which catalyzes the reversible conversion of 5 alpha-dihydroprogesterone (5 alpha-DHP) to 3 alpha, 5 alpha-tetrahydroprogesterone (3 alpha, 5 alpha-THP) has been characterized in terms of its steroid substrate specificity, dihydrodiol dehydrogenase activity and inhibition by drugs such as medroxyprogesterone and indomethacin. The purified enzyme has a strong preference for the C21 progestin steroid substrates, 5 alpha-DHP and 3 alpha, 5 alpha-THP, over the corresponding C19 androgenic steroid substrates, 5 alpha-dihydrotesterone (5 alpha-DHT) and 3 alpha, 5 alpha-tetrahydrotestosterone (3 alpha, 5 alpha-THT). The apparent Km for 5 alpha-DHP (80 nM) is about 250 times lower than the Km for the androgenic steroid, 5 alpha-DHT (21 microM). In the oxidative direction, the apparent Km for 3 alpha, 5 alpha-TP (1.4 microM) is about 3-fold lower than the Km for the androgenic steroid, 3 alpha, 5 alpha-THT (4.2 microM). A number of other naturally occurring 3-keto- and 3 alpha(beta)-hydroxy-steroids were assessed for their ability to act as inhibitors (alternate substrates) of the 3 alpha-reduction of 5 alpha-DHP catalyzed by the purified 3 alpha-HSOR. None of the 3 beta- or 5 beta-isomers had any effect. Of the other 3-keto and 3 alpha- steroids tested, only deoxycorticosterone and the ovarian progestins showed any significant inhibition. These may be acting as inhibitors since there was little, if any, direct 3 alpha-reduction of progesterone to 3 alpha-hydroxy-4-pregnen-20-one. Unlike the liver cytosolic 3 alpha-HSOR, the pituitary enzyme has no associated dihydrodiol (quinone) dehydrogenase activity. This enzyme is similar to other cytosolic 3 alpha-HSORs from liver and brain in that it is potentially inhibited by indomethacin and by medroxyprogesterone.

3-Hydroxysteroid Dehydrogenases↗