Studies on the biosynthesis of 16-dehydro steroids. The metabolism of [4-14C]pregnenolone by boar adrenal and testis tissue in vitro.
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ABSTRACT:
SUBMITTER: Gower DB
PROVIDER: S-EPMC1270619 | biostudies-other | 1967 Aug
REPOSITORIES: biostudies-other
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Project description:1. The formation of androst-16-enes from [4-(14)C]progesterone has been investigated with long-term incubations and short-term kinetic studies. After 4hr., 1.7 and 10.3% respectively of 3alpha- and 3beta-hydroxy-5alpha-androst-16-enes were formed in boar testis minces, but much smaller yields were obtained in boar adrenal. Both tissues formed small quantities of androsta-4,16-dien-3-one. 2. The amounts of androst-4-ene-3,17-dione and testosterone isolated were small, suggesting that androst-16-ene formation may occur preferentially in the boar testis. 3. In the absence of tissue no radioactive androst-16-enes were formed. 4. Incubation of both [4-(14)C]pregnenolone and [7alpha-(3)H]progesterone resulted in 3alpha- and 3beta-hydroxy-5alpha-androst-16-enes containing (3)H/(14)C ratios of near unity and confirmed that both C(21) steroids were precursors. A similar incubation with 17alpha-hydroxy[4-(14)C]-progesterone and [7alpha-(3)H]progesterone gave the same Delta(16)-alcohols, but they contained only (3)H, indicating that side-chain cleavage of pregnenolone and progesterone occurred before 17alpha-hydroxylation. 5. Dehydroepiandrosterone, testosterone, testosterone acetate and 16-dehydroprogesterone were not found to be precursors of Delta(16)-steroids. 6. A pathway is proposed for the biosynthesis of 3alpha- and 3beta-hydroxy-5alpha-androst-16-enes from pregnenolone and progesterone; this may involve androsta-4,16-dien-3-one as an intermediate, but excludes 17alpha-hydroxyprogesterone, testosterone and dehydroepiandrosterone.
| S-EPMC1198798 | biostudies-other
Project description:1. The formation of the two 16-unsaturated alcohols 5alpha-androst-16-en-3alpha-ol and 5alpha-androst-16-en-3beta-ol from [5alpha-(3)H]5alpha-androst-16-en-3-one has been demonstrated in boar testis homogenates. 2. The optimum yield (23%) of the 3alpha-alcohol was obtained in the presence of NADPH, whereas that for the 3beta-alcohol (74%) was obtained when NADH was the added cofactor. 3. The two alcohols were not interconvertible. 4. Prolonged storage of boar testis tissue at -20 degrees C abolished the ability to form all androst-16-enes except androsta-4,16-dien-3-one from [4-(14)C]progesterone. 5. The production of 5alpha-androst-16-en-3-one and the two alcohols from [7alpha-(3)H]androsta-4,16-dien-3-one only occurred when fresh tissue was used, whereas reduction of [5alpha-(3)H]5alpha-androst-16-en-3-one was unaffected by storage of testis at -20 degrees C. 6. NADPH was the preferred cofactor for the reduction of androsta-4,16-dien-3-one. 7. The previously established conversion of androsta-5,16-dien-3beta-ol into androsta-4,16-dien-3-one was shown to be reversible, NADH and NADPH being equally effective cofactors. 8. Pathways of biosynthesis of 5alpha-androst-16-en-3alpha- and 3beta-ols, with the C(19) 3-oxo steroids as intermediates, are presented.
| S-EPMC1173914 | biostudies-other
Project description:1. The metabolism of [4-(14)C]pregnenolone to androst-16-enes has been studied in short-term incubations of boar testis tissue. With fresh tissue androsta-5,16-dien-3beta-ol (8%) and 5alpha-androst-16-en-3beta-ol (2%) were formed. Tissue that had been stored at -20 degrees C was still capable of metabolizing pregnenolone to androsta-5,16-dien-3beta-ol. 2. NADPH was essential for the formation of androsta-5,16-dien-3beta-ol from pregnenolone; NADH had less activity and ATP was not necessary for the reaction. 3. [4-(14)C]Androsta-5,16-dien-3beta-ol, prepared biosynthetically from [4-(14)C]pregnenolone, was shown to be converted by boar testis preparations into androsta-4,16-dien-3-one (31%) if NAD(+) was present or into 5alpha-androst-16-en-3beta-ol (4%) if NADPH was present. 4. 17alpha-Hydroxyandrost-4-en-3-one and 3beta,17alpha-dihydroxypregn-5-en-20-one were considered as possible precursors for androst-16-ene formation, but both were shown to be ineffective. 5. No radioactivity was incorporated into androst-5-en-3beta-ol used to trap any corresponding (14)C-labelled compound formed from [4-(14)C]pregnenolone.
| S-EPMC1178957 | biostudies-other
Project description:1. The possible involvement of 5-pregnene-3beta,20beta-diol in 16-unsaturated C(19) steroid biosynthesis has been investigated. 2. 5,16-Androstadien-3beta-ol (andien-beta) formation from [4-(14)C]pregnenolone (3beta-hydroxy-5-pregnen-20-one), 5-pregnene-3beta,20alpha-diol and 5-pregnene-3beta,20beta-diol was studied in homogenates of boar testis and the mean yields obtained were 25.6, 2.7 and 16.0% respectively. 3. Short-term kinetic studies with pregnenolone and 5-pregnene-3beta,20beta-diol separately and together suggested that the latter compound might be an intermediate in the biosynthesis of andien-beta. 4. In agreement with this interpretation, radioactive 5-pregnene-3beta,20beta-diol has been isolated during andien-beta biosynthesis from [4-(14)C]pregnenolone in the presence of NADPH, more radioactivity being trapped under limiting conditions of andien-beta formation with NADH present as cofactor. 5. Further, 5-pregnene-3beta,20beta-diol and andien-beta have been shown to inhibit the formation of the 16-unsaturated C(19) steroid from [4-(14)C]pregnenolone, the yield of radioactive 5-pregnene-3beta,20beta-diol increasing in the presence of added unlabelled andien-beta. 6. It is concluded that there may be two pathways leading to 16-unsaturated C(19) steroid formation from pregnenolone, one of these involving 5-pregnene-3beta,20beta-diol as an intermediate. Possible mechanisms are presented and discussed.
| S-EPMC1178696 | biostudies-other
Project description:1. In one experiment [7alpha-(3)H]pregnenolone was infused continuously for 12min into the left spermatic artery of a sexually mature boar and blood was collected during this period by continuous drainage from the spermatic vein. After infusion, the testis was removed and immediately cooled to -196 degrees C. 2. From both the testicular tissue and the spermatic venous plasma, (3)H-labelled 16-unsaturated C(19) steroids were isolated and characterized and their radiochemical purity was established. 5alpha-Androst-16-en-3alpha- and 3beta-ol occurred mainly as sulphate conjugates and to a lesser extent as free steroids. Only traces of these alcohols occurred as glucosiduronate conjugates. 5alpha-Androst-16-en-3-one was found in the free (ether-extractable) fraction. 3. The isotope concentration of each of the (3)H-labelled 16-unsaturated C(19) steroids in testicular tissue was different from that in spermatic venous plasma. 4. The ratios of tritiated 5alpha-androst-16-en-3alpha- and 3beta-ol (free steroids) to their respective sulphate conjugates in the testicular tissue were less than the ratios of the same compounds in the spermatic venous plasma. The possibility that the sulphates are partially hydrolysed by testicular sulphatases before secretion is discussed. 5. In a second experiment, a continuous close-arterial infusion of [7alpha-(3)H]pregnenolone into the left testis was performed over a 200min period and all the urine that accumulated during the infusion was collected for analysis. 6. No (3)H-labelled 16-unsaturated C(19) steroids were detected in the urine as free steroids. Only a trace of 5alpha-androst-16-en-3alpha-ol was detected conjugated as glucosiduronate, whereas the corresponding 3beta-alcohol occurred mainly as glucosiduronate and to a lesser extent as sulphate. 7. The absence of 5alpha-androst-16-en-3beta-ol glucosiduronate in the spermatic venous blood and its presence in considerable amount in the urine may be attributed to hepatic glucuronyl transferase activity.
| S-EPMC1174167 | biostudies-other
Project description:A mycelial culture of the Kenyan basidiomycete Fomitiporia aethiopica was fermented on rice and the cultures were extracted with methanol. Subsequent HPLC profiling and preparative chromatography of its crude extract led to the isolation of five previously undescribed pregnenolone type triterpenes 1-5, for which we propose the trivial name aethiopinolones A-E. The chemical structures of the aethiopinolones were determined by extensive 1D- and 2D-NMR, and HRMS data analysis. The compounds exhibited moderate cytotoxic effects against various human cancer cell lines, but they were found devoid of significant nematicidal and antimicrobial activities.
| S-EPMC6017562 | biostudies-literature
Project description:In humans, the precursor to all steroid hormones, pregnenolone, is synthesized from cholesterol by an enzyme complex comprising adrenodoxin reductase (AdR), adrenodoxin (Adx), and a cytochrome P450 (P450scc or CYP11A1). This complex not only plays a key role in steroidogenesis, but also has long been a model to study electron transfer, multistep catalysis, and C-C bond cleavage performed by monooxygenases. Detailed mechanistic understanding of these processes has been hindered by a lack of structural information. Here we present the crystal structure of the complex of human Adx and CYP11A1--the first of a complex between a eukaryotic CYP and its redox partner. The structures with substrate and a series of reaction intermediates allow us to define the mechanism underlying sequential hydroxylations of the cholesterol and suggest the mechanism of C-C bond cleavage. In the complex the [2Fe-2S] cluster of Adx is positioned 17.4 Å away from the heme iron of CYP11A1. This structure suggests that after an initial protein-protein association driven by electrostatic forces, the complex adopts an optimized geometry between the redox centers. Conservation of the interaction interface suggests that this mechanism is common for all mitochondrial P450s.
| S-EPMC3121847 | biostudies-literature
Project description:Arachidonic acid (ARA) is one of the most abundant polyunsaturated fatty acids (PUFAs) in the mammalian brain. Many enzymatically- and nonenzymatically-produced metabolic products have important and potent pharmacological properties. However, uniformly isotope labeled forms of ARA are not commercially available for studying the metabolic fates of ARA. This study describes a simple and efficient protocol for the biosynthesis of U-13C-ARA from U-13C-glucose, and U-14C-ARA from U-14C-glucose by Mortierella alpina. The protocols yield approximately 100nmol quantities of U-13C-ARA with an isotopic purity of 95% from a 500?l batch volume, and approximately 2?Ci quantities of U-14C-ARA with an apparent specific activity in excess of 1200Ci/mol from a 250?l batch volume.
| S-EPMC5237611 | biostudies-literature
Project description:Cytochrome P450s (CYPs) are an essential family of enzymes in the human body. They play a crucial role in metabolism, especially in human steroid biosynthesis. Reactions catalyzed by these enzymes are highly stereo- and regio-specific. Lack or severe malfunctions of CYPs can cause severe diseases and even shorten life. Hence, investigations on metabolic reactions and structural requirements of substrates are crucial to gain further knowledge on the relevance of different enzymes in the human body functions and the origin of diseases. One key enzyme in the biosynthesis of gluco- and mineralocorticoids is CYP21A2, also known as steroid 21-hydroxylase. To investigate the steric and regional requirements of substrates for this enzyme, we performed whole-cell biotransformation assays using a strain of fission yeast Schizosaccharomyces pombe recombinantly expressing CYP21A2. The progestogens progesterone, pregnenolone, and their 17α-hydroxy-derivatives were used as substrates. After incubation, samples were analyzed using gas chromatography coupled to mass spectrometry. For progesterone and 17α-hydroxyprogesterone, their corresponding 21-hydroxylated metabolites 11-deoxycorticosterone and 11-deoxycortisol were detected, while after incubation of pregnenolone and 17α-hydroxypregnenolone, no hydroxylated product was observed. Findings were confirmed with authentic reference material. Molecular docking experiments agree with these results and suggest that interaction between the 3-oxo group and arginine-234 of the enzyme is a strict requirement. The presented results demonstrate once more that the presence of an oxo-group in position 3 of the steroid is indispensable, while a 3-hydroxy group prevents hydroxylation in position C-21 by CYP21A2. This knowledge may be transferred to other CYP21A2 substrates and hence help to gain essential insights into steroid metabolism.
| S-EPMC8211424 | biostudies-literature
Project description:1. 26-Hydroxycholesterol was obtained by reducing the methyl ester of (+/-)-3beta-hydroxycholest-5-en-26-oic acid, which was synthesized from 25-oxonorcholesterol. 2. Methods for preparing 7alpha-hydroxycholesterol and 7-dehydrocholesterol were modified to allow the micro-scale preparation of these [(14)C]sterols from [26-(14)C]-cholesterol. 3. 26-Hydroxycholesterol was oxidized more readily than 7alpha-hydroxycholesterol, 7-dehydrocholesterol or cholesterol by mitochondrial preparations from livers of mice, rats, guinea pigs, common toads (Bufo vulgaris) and Caiman crocodylus. 4. (+/-)-3beta-Hydroxy[26-(14)C]cholest-5-en-26-oic acid was oxidized very rapidly to (14)CO(2) by mouse and guinea-pig mitochondria without evident discrimination between the two optical isomers. 5. An enzyme system that oxidizes 26-hydroxycholesterol to 3beta-hydroxycholest-5-en-26-oic acid was identified in the soluble extract of rat-liver mitochondria. This enzyme could use NADP in place of NAD but was not identical with liver alcohol dehydrogenase (EC 1.1.1.1). 6. [26-(14)C]Cholesteryl 3beta-sulphate was not oxidized by fortified mouse-liver preparations that oxidized [26-(14)C]cholesterol to (14)CO(2).
| S-EPMC1264860 | biostudies-other