scholarly journals Mechanistic and stereochemical studies on 3-oxo steroid Δ4-Δ5-isomerase from human placenta

1980 ◽  
Vol 185 (2) ◽  
pp. 411-421 ◽  
Author(s):  
M Akhtar ◽  
M Calder ◽  
T Smith ◽  
J N Wright
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Human Placenta ◽  
Microsomal Fraction ◽  
Isomerization Reaction ◽  
Acidic Group ◽  
Incoming Proton ◽  
Membrane Bound ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

The mechanism of isomerization of delta 5-3-ox steroids to delta 4-3-oxo steroids was examined by using the membrane-bound 3-oxo steroid delta 4-delta 5-isomerase (EC 5.3.3.1) and the 3 beta-hydroxy steroid dehydrogenase present in the microsomal fraction obtained from full-term human placenta. (1) Methods for the preparation of androst-5-ene-3 beta, 17 beta-diol specifically labelled at the 4 alpha-, 4 beta- or 6-positions are described. (2) Incubations with androst-5-ene-3 beta, 17 beta-diol stereospecifically 3H-labelled either in the 4 alpha- or 4 beta-position showed that the isomerization reaction occurs via a stereospecific elimination of the 4 beta hydrogen atom. In addition, the complete retention of 3H in the delta 4-3-oxo steroids obtained from [4 alpha-3H]androst-5-ene-3 beta, 17 beta-diol indicates that the non-enzymic contribution to these experiments was negligible. (3) To study the stereochemistry of the insertion of the incoming proton at C-6, the [6-3H]androst-4-ene-3, 17-dione obtained from the oxidation isomerization of [6-3H]androst-5-ene-3 beta, 17 beta-diol was enzymically hydroxylated in the 6 beta-position by the fungus Rhizopls stolonifer. Retention of 3H in the 6 alpha-position of the isolated 6 beta-hydroxyandrost-4-ene-3, 17-dione indicates that in the isomerase-catalysed migration of the C(5) = C(6) double bond, the incoming proton from the acidic group on the enzyme must enter C-6 from the beta-face, forcing the existing 3H into the 6 alpha-position.

Changes in the Abundance of mRIMA for Type-l 3β-Hydroxy-steroid Dehydrogenase/Δ5→Δ4Isomerase in the Human Placenta and Fetal Membranes during Pregnancy and Labor

1993 ◽  
Vol 35 (4) ◽  
pp. 199-203 ◽  
Author(s):  
Simon C. Riley ◽  
Nicole S. Bassett ◽  
Edward T.M. Berdusco ◽  
Kaiping Yang ◽  
Cheryl Leystra-Lantz ◽  
...  
Keyword(s):  
Human Placenta ◽  
Fetal Membranes ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

scholarly journals 3β-Hydroxy steroid dehydrogenase activity in the mitochondria of rat adrenal homogenates

1971 ◽  
Vol 125 (4) ◽  
pp. 983-989 ◽  
Author(s):  
R S Basch ◽  
M J Finegold
Keyword(s):  
Electron Microscopy ◽  
Microsomal Fraction ◽  
Total Activity ◽  
Mitochondrial Fraction ◽  
Differential Centrifugation ◽  
Radioisotopic Method ◽  
Cell Fractions ◽  
Kinetics Of ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

The activity of 3β-hydroxy steroid dehydrogenase (EC 1.1.1.51) in the mitochondrial fraction of rat adrenal homogenates was approx. 31% of the total activity recovered after differential centrifugation and washing of the particulate fractions. Some 45% of the total activity was found in the microsomal fraction. The activity was assayed by a radioisotopic method devised in this laboratory for the purpose of studying small quantities of tissue and cell fractions. Satisfactory separation of the two fractions was demonstrated by electron microscopy of the pellets and by comparative recoveries of RNA, steroid 21-hydroxylase and cytochrome c oxidase in the various compartments. Analyses of the kinetics of the enzyme activity in the two fractions revealed no significant differences in apparent Km for pregnenolone, dehydroepiandrosterone or NAD+, but demonstrated a distinct difference in the Km for NADP+. pH optima and susceptibility to cyanoketone inhibition were similar in both fractions.

scholarly journals Metabolism of androst-4-ene-3,17-dione by subcellular fractions of rat adrenal tissue with particular reference to microsomal C19-steroid 5α-reductase

1973 ◽  
Vol 132 (2) ◽  
pp. 283-291 ◽  
Author(s):  
Paul V. Maynard ◽  
Euan H. D. Cameron
Keyword(s):  
Cytochrome C ◽  
Microsomal Fraction ◽  
Soluble Fraction ◽  
Subcellular Fractions ◽  
Dehydrogenase System ◽  
Separate System ◽  
Hydroxy Steroid ◽  
Microsomal Pellet ◽  
Steroid Dehydrogenase

The location and some characteristics of rat adrenal C19-steroid 5α-reductase were investigated by using [7α-3H]androst-4-ene-3,17-dione and [7α-3H]testosterone as substrates. The enzymes system was shown to be NADPH-dependent and associated with the microsomal fraction. In addition, some evidence was also obtained for the existence of a separate NADH-dependent system in the soluble fraction. Further investigation of androst-4-ene-3,17-dione metabolism by subcellular fractions indicated the presence of NADH-dependent 3α- and 3β-hydroxy steroid dehydrogenase systems in the microsomal pellet. This pellet also appeared to contain an NADH-dependent 17β-hydroxy steroid dehydrogenase system, and a similar though separate system was detected in the cytosol. Malate (20mm) effectively inhibited the microsomal C19-steroid 5α-reductase, which showed similar values for Km and Vmax. when either androst-4-ene-3,17-dione or testosterone was used as substrate. Cytochrome c was added to all incubation mixtures used for the determination of these values to inhibit the formation of metabolites other than 5α-androstane-3,17-dione and 5α-dihydrotestosterone (17β-hydroxy-5α-androstan-3-one) respectively. It was also found that corticosterone did not inhibit the 5α-reduction of androst-4-ene-3,17-dione under these conditions, indicating that separate enzymes exist for the 5α-reduction of C19- and C21-steroids in the rat adrenal.

A metabolic stability determination of Tetrahydrothiazolopyridine derivative a selective 11β-hydroxy steroid dehydrogenase type 1 (11β-hsd1) inhibitor

2017 ◽  
Vol 8 (3) ◽  
Author(s):  
MURUGESH KANDASAMY ◽  
MUHAMMED SALIHIN ◽  
MALLIKARJUNA RAO PICHIKA ◽  
SLAVKO KOMARNYTSKY ◽  
THIRUMURUGAN RATHINASABAPATHY
Keyword(s):  
Metabolic Stability ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

DIFFICULTIES IN THE DIAGNOSIS OF THE ADRENOGENITAL SYNDROME IN INFANCY

PEDIATRICS ◽  
1972 ◽  
Vol 49 (2) ◽  
pp. 198-205
Author(s):  
C. H. Shackleton ◽  
F. L. Mitchell ◽  
J. W. Farquhar
Keyword(s):  
Hydroxylase Deficiency ◽  
Adrenogenital Syndrome ◽  
Steroid Excretion ◽  
21 Hydroxylase Deficiency ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

Pregnanetriol was not excreted by an infant (7 days old) who was later shown to have a defect in steroid 21-hydroxylase. However, the excretion of this compound increased during the following days (1.2 mg on the thirteenth day of life). A high excretion of 3β-hydroxy-Δ steroids was the most noticeable abnormality in steroid excretion noted on the seventh day of life (e.g., 3β, 16α-dihydroxy-5-pregnen-20-one, 15 mg; 3β, 21-dihydroxy-5-pregnen-20-one, 1.4 mg and 3β, 16α-dihydroxy-5-androsten-17-one, 7.4 mg). This high 3β-hydroxy-Δ steroid excretion results in difficulties in distinguishing a defect in 3β-hydroxy steroid dehydrogenase from a 21-hydroxylase deficiency. At the age of 14 months the principal steroids excreted were those predominant in other cases of 21-hydroxylase deficiency, viz. pregnanetriol and 5β-pregnane-3α, 17α, 20α-triol-11-one (11-oxo-pregnanetriol).

Sulfur Vulcanization of Simple Model Olefins, Part V: Double Bond Isomerization during Accelerated Sulfur Vulcanization as Studied by Model Olefins

1997 ◽  
Vol 70 (1) ◽  
pp. 106-119 ◽  
Author(s):  
P. Versloot ◽  
J. G. Haasnoot ◽  
P. J. Nieuwenhuizen ◽  
J. Reedijk ◽  
M. van Duin ◽  
...  
Keyword(s):  
Double Bond ◽  
Isomerization Reaction ◽  
Radical Mechanism ◽  
Formation Mechanisms ◽  
Molecular Models ◽  
Tetramethylthiuram Disulfide ◽  
Alkyl Substitution ◽  
Sulfur Vulcanization ◽  
The One ◽  
Vulcanization Process

Abstract The sulfur vulcanization of unsaturated rubber has been studied with the use of various olefins as simple, low-molecular models. By treatment of these olefins with a mixture of zinc oxide, sulfur, and tetramethylthiuram disulfide (TMTD) at 140 °C, a mixture of dialkenyl sulfides is obtained mimicking crosslinked rubber. Isomerization of the double bond may take place during this reaction, depending on the olefin used. The position of the double bond is on the one hand determined by crosslink formation mechanisms, and on the other hand by isomerization, which takes place at higher temperatures. The position of the equilibrium between isomeric alkenyl sulfides is determined by the increased stability of the sulfide which in itself results from an increased degree of alkyl substitution at the unsaturation. Due to the isomerization reaction, at higher temperatures no mechanism for crosslink formation can be discerned. At room temperature, however, a radical mechanism appears to be predominant during the vulcanization process.

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