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Biomedical subjects

L L Engel

Publications and source records attributed to L L Engel.

At least 19 recordsLinked to original sources
PubMed1979

Circannual variation and genetic regulation of hepatic testosterone hydroxylase activities in inbred strains of mice.

Hydroxylation of testosterone by hepatic microsomes at positions 6 alpha, 6 beta, 7 alpha, 15 alpha, and 16 alpha has been studied in C57BL/6J, 129/J, and A/J mice. Differences in hydroxylase activities between the C57BL/6J and A/J strains and between the C57BL/6J and 129/J strains were investigated using standard genetic breeding protocols. In the C57BL/6J X A/J line, 6 alpha- and 7 alpha-hydroxylase activity appeared to be under polygenic control in both sexes, as did 15 alpha-hydroxylase activity in females. The lack of 16 alpha-hydroxylase activity observed in 129/J females behaved as a recessive, autosomal, single locus, sex-limited trait. In several instances, the level of hydroxylase activity at one position appeared to be affected by the level of hydroxylase activity at a second position; however, no clear-cut pattern was discerned. Over a period of a year, a remarkable cycle in total hydroxylase activity for all mice was observed; the average activity was greatest in December and least in April.

Animals↗
PubMed1978

The mass spectra of diethylstilbestrol and related compounds.

The low resolution mass spectra of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene (diethylstilbestrol), E-[1,1,1-3H3]3,4-bis-(p-hydroxyphenyl)-hex-3-ene, E-2,3-bis-(p-hydroxyphenyl)-but-2-ene (dimethylstilbestrol), E,E-3,4-bis-(p-hydroxyphenyl)hexa-2,4-diene (dienestrol) and 3,4-bis-(p-hydroxyphenyl)-hexane (hexestrol) were examined as the parent compounds, their diacetates, dimethyl ethers, and bis-trimethylsilyl ethers. In addition, the mass spectra of the diethyl ether and the hexadeuteriodimethyl ether of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene were studied. Each compound gives rise to several sets of characteristic fragment ions associated with loss of alkyl groups, loss of aryl groups and rearrangements. An ion of m/e 165 (C13H9) was found in the spectra of all the compounds studied. With the aid of high resolution mass spectrometry empirical formulae were assigned to major ions of the free diphenols.

Adenocarcinoma↗
PubMed1978

Metabolism of diethylstilbestrol: identification of a catechol derived from dienestrol.

The enzymatic oxidation of E-3,4-bis-(p-hydroxyphenyl)-hex-3-ene (diethylstilbestrol) by either mushroom tyrosinase or rat liver microsomes in the presence of NADPH and air yields a catechol. Upon further oxidation of both compounds with periodate and condensation of the resulting o-quinones with o-phenylenediamine, phenazines are produced. The phenazines derived from the products of both the plant and animal enzyme systems are identical to the product obtained by oxidation of diethylstilbestrol with potassium nitrosodisulfonate and condensation of the o-quinone produced with o-phenylenediamine. High and low resolution mass spectra of the phenazine are consistent with its derivation from a catechol having two fewer hydrogens than diethylstilbestrol.

Animals↗
PubMed1977

Hydroxysteroid dehydrogenases of Pseudomonas testosteroni. Separation of a 17 beta-hydroxysteroid dehydrogenase from the 3(17) beta-hydroxysteroid dehydrogenase and comparison of the two enzymes.

When a crude extract of Pseudomonas testosteroni induced with testosterone was subjected to polyacrylamide gel electrophoresis, six bands that stained for 17 beta-hydroxysteroid dehydrogenase activity was observed. A protein fraction containing the enzyme corresponding to the fastest migrating band and devoid of the other hydroxysteroid dehydrogenase activities has been obtained. This preparation appears to be distinct from the previously isolated 3(17) beta-hydroxysteroid dehydrogenase (EC 1.1.1.51) in its chromatography properties on DEAE-cellulose, substrate and cofactor specificity, immunological properties and heat stability. The preparation appears devoid of 3alpha-, 3beta-, 11beta-, 17alpha-, 20alpha-, and 20beta-hydroxysteroid dehydrogenase activities. The enzyme transfers th 4-pro-S-hydrogen of NADH from estradiol-17beta (1,3,5(10)estratriene-3,17beta-diol) to estrone (3-hydroxy-1,3,5(10)-estratriene-17-one).

17-Hydroxysteroid Dehydrogenases↗
PubMed1977

3(17)beta-Hydroxysteroid Dehydrogenase of Pseudomonas testosteroni. Ligand binding properties.

The binding of NAD and NADH to electrophoretically pure 3(17)beta-hydroxysteroid dehydrogenase of Pseudomonas testosteroni was determined by Fluorescence spectroscopy and gel filtration. Four moles of cofactor are bound/mol of tetrameric enzyme; the binding sites are equivalent and independent. The dissociation constants for NAD and NADH are 16 and 0.25 micronM, respectively. As measured by gel filtration in the absence of cofactor, 0.4 mol of estradiol-17 beta is bound/mol of tetrameric enzyme. Data obtained from isotope exchange at equilibrium indicate that the binding of the cofactor to the enzyme is favored over the binding of steroid, although each may bind in the absence of the other. The rates of cofactor dissociation from the ternary complexes are slower than the rates of steroid dissociation; cofactor dissociation is probably the rate-limiting step. Cofactor analogs modified in the pyridine moiety are cosubstrates, whereas modified adenine derivatives are not. The enzyme also utilized as substrate a number of potential steroid affinity labels; no enzyme inactivation by these compounds was observed.

Binding Sites↗
PubMed1976

Horse-liver alcohol dehydrogenase and Pseudomonas testosteroni 3(17)beta-hydroxysteroid dehydrogenase transfer epimeric hydrogens from NADH to 17beta-hydroxy-5alpha-androstan-3-one. An exception to one of the Alworth-Bentley rules.

In the reduction of 17beta-hydroxy-5alpha-androstan-3-one to the 3beta-alcohol, horse liver alcohol dehydrogenase utilizes the 4-pro-R hydrogen of NADH whereas the 3(17)beta-hydroxysteroid dehydrogenase of Pseudomonas testosteroni utulized the 4-pro-S hydrogen. These observations provide an exception to the rule proposed by Alworth and Bentley that with regard to the paired methylene hydrogens at C-4 of NADH and NADPH "the stereospecificity of a particular reaction is fixed and does not vary with the source of the enzyme preparation". It is also apparent that for these two enzymes, the selection of the side of NADH from which hydride is transferred to substrate cannot in both cases be dictated by the "best fit" of substrate and cofactor.

Alcohol Oxidoreductases↗
PubMed1976

Metabolism of diethylstilbestrol by rat liver: a preliminary report.

Aerobic incubation of a misture of E[1,1,1-D3]-3,4;bis(p-hydroxyphenyl)-hex-3-ene admixed with an approximately equimolar amount of unlabeled diethylstilbestrol and [ 2-(14)C ] diethylstilbestrol with rat liver homogenates in the presence of NADPH yielded water-soluble metabolites as well as products more and less polar than the starting material. Addition of 5-adenosyl-L-methionine increased the quantity of nonpolar metabolites. Incubation with rat liver microsomes yielded similar results. When polar metabolites from incubation with rat liver microsomes were incubated with catechol O-methyltransferase and S-adenosyl[methyl-3 H]-L-methionine there was conversion to 3H-labeled nonpolar products. Examination of reaction products by means of gas chronatography-mass spectrometry gave evidence for the formation of a dihydroxydiethylstilbestrol, a dihydroxydienestrol, and a monomethoxydiethylstilbestrol.

Animals↗
PubMed1975

Hydroxylation of testosterone at carbons 1, 2, 6, 7, 15 and 16 by the hepatic microsomal fraction from adult female C57BL/6J mice.

The metabolism of a mixture of [4-14C]- and [7 beta-2H]testosterone by the hepatic microsomal fraction from adult femal C57BL/6J mice has been investigated. The following metabolites were identified by their mass spectra and by their retention times on gas chromatography on one or two phases: 1epsilon-, 2beta-, 6alpha-, 6beta-, 7alpha-, 15alpha-, 15beta-, 16alpha- and 16beta-hydroxytestosterone; 6alpha-, 6beta- and 7alpha-hydroxy-4-androstene-3,17-dione; and 4-androstene-3,17-dione. A compound tentatively identified as 6- or 7-oxotestosterone was also isolated. 17beta-Hydroxy-4,6-androstadien-3-one, 17beta-hydroxy-1,4-androstadien-3-one and 4,6-androstadiene-3,17-dione were identified but are considered to arise non-enzymatically from 7alpha-hydroxytestosterone, 1epsilon-hydroxytestosterone and 7alpha-hydroxy-4-androstene-3,17-dione, respectively.

Acclimatization↗
PubMed1975

Catalytic competence, a new criterion for affinity labeling. Demonstration of the reversible enzymatic interconversion of estrone and estradiol-17 beta covalently bound to human placental estradiol-17 beta dehydrogenase.

Human placental estradiol-17beta dehydrogenase is rapidly inactivated upon treatment with 3-bromoacetoxyestrone. Pseudo-first order kinetic data are obtained and inactivation is accompanied by incorporation of 1 mol of 3-acetoxyestrone/mol of subunit (Mr =34,000). Treatment of the inactivated enzyme with (4S)-[4-2H]DPNH results in the formation of covalently bound [17alpha-2H]estradiol-17beta, which can be released by hydrolysis and identified by gas chromatography-mass sepctrometry. When (4R)-[4-2H]DPNH was used, deuterium was not transferred. Thus, the normal stereochemistry of hydridetransfer is preserved for both partners. After treatment with p-mercuribenzoate, affinity-labeled estradiol-17beta dehyrogenase is no longer able to caralyze reduction its covalently bound estrone; in the presence of DPNH and native enzyme, however, reduction occurs, demonstrating that affinity-labeled enzyme can itself serve as subtrate for native estradiol-17beta dehydrogenase. The reversible enzymatic interconversion of covalently bound estrone was demonstrated using a transhydrogenase assay. The ability of an enzyme to catalyze its normal reaction with a covalently bound substrate is termed catalytic competence, and is considered to be a new criterion for affinity labeling.

Affinity Labels↗