Mass spectrometry of steroid systems–V

Zaretskii, V. I.; Wulfson, N.S.; Заикин, В. Г.; Kogan, L. M.; Voischvillo, N.E.; Torgov, I. V.

doi:10.1016/s0040-4020(01)99435-9

Cited by 46 publications

(7 citation statements)

References 7 publications

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“…The first eluting product showed a parent ion at m/z 346 (M+, 8% relative abundance) and the following daughter ions: 328 (M+ -H20, 19%), 313 (M+ -CH3 -H20, 13%), 285 (M+ -H20 -COCH3, 18%), 247 (M+ -C502H7, 30%), 100 (C502H8+, 28%), and 43 (COCH3+, 100%). The molecular weight of the parent ion is consistent with a dihydroxy metabolite; the daughter ion at m/z 100 was reported by Zaretskii et al (1966) to be formed from a fragment ion which includes carbons 15, 16, and 17 of the steroid D ring and the substituents bound to these atoms when a hydroxy group is bound to the 15/3-or 16a-positions. The daughter ion at m/z 247 indicates the other hydroxyl group is located on the A, B, or C rings of the steroid.…”

Section: Resultssupporting

confidence: 55%

Evidence for concerted kinetic oxidation of progesterone by purified rat hepatic cytochrome P-450g

Swinney¹,

Ryan²,

Thomas³

et al. 1988

Biochemistry

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Purified cytochrome P-450g, a male-specific rat hepatic isozyme, was observed to metabolize progesterone to two primary metabolites (6 beta-hydroxyprogesterone and 16 alpha-hydroxyprogesterone), two secondary metabolites (6 beta,16 alpha-dihydroxyprogesterone and 6-ketoprogesterone), and one tertiary metabolite (6-keto-16 alpha-hydroxyprogesterone). The Km,app for the formation of these products from progesterone was determined to be approximately 0.5 microM, while the Km,app for metabolism of 6 beta- and 16 alpha-hydroxyprogesterone was found to be 5-10 microM. The ratio of primary to secondary metabolites did not change significantly at progesterone concentrations from 6 to 150 microM, and a lag in formation of secondary metabolites was not observed in 1-min incubations. Concerted oxidation of progesterone to secondary products without the intermediate products leaving the active site was suggested by these results and confirmed by isotopic dilution experiments in which little or no dilution of metabolically formed 6 beta,16 alpha-dihydroxyprogesterone and 6-keto-16 alpha-hydroxyprogesterone was observed in incubations containing a mixture of radiolabeled progesterone and unlabeled 6 beta-hydroxyprogesterone or 16 alpha-hydroxyprogesterone. Incubation of 6 beta-hydroxyprogesterone with a reconstituted system in an atmosphere of 18O2 resulted in greater than 90% incorporation of 18O in the 16 alpha-position of 6 beta,16 alpha-dihydroxyprogesterone but no incorporation of 18O into 6-ketoprogesterone, even though the reaction was dependent upon enzyme and O2, and not inhibited by mannitol, catalase, or superoxide dismutase. Factors which characterize the metabolism of progesterone by cytochrome P-450g in terms of active-site constraints and the catalytic competence of the enzyme in microsomes were also explored.

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Section: Resultssupporting

confidence: 55%

Evidence for concerted kinetic oxidation of progesterone by purified rat hepatic cytochrome P-450g

Swinney¹,

Ryan²,

Thomas³

et al. 1988

Biochemistry

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“…The present p a p shows that the dislocations introduccd into the crystal undcr the above conditions have a total Burgers vector of ( 4 2 ) (110) type. This sufficiently dcnionstratcs thc validity of the assumptions made in 12, 141 that plastic deformation of ZnSe in the specimen geometry irscd is realized by total dislocations with Burgers vectors (c2/2) (1 lo). I t follows froin selective etching of plastically defornicd specinicns of ZnSe that the mobility of 60" Se(g) dislocations considerably excccds that of other dislocations of ( 4 2 ) (110) type 1141.…”

Section: Disciimionmentioning

confidence: 51%

Dislocations in deformed ZnSe single crystals as studied by Weak-beam electron microscopy

Аристов

Zaretskii

Osip’yan

et al. 1983

Phys. Stat. Sol. (a)

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“…15/3-OHP was isolated by HPLC (system I) and showed suitable chromatographic properties; the electron impact mass spectrum was identical with published spectra (Zaretskii et al, 1966): m/z 231 (M+ -C5H702), 269 (M+ -H20 -CH3CO), 312 (M+ -H20), 330 (M+). The ratio of m/z 330 to 312 was 0.25 ± 0.13, which is consistent with the literature value of 0.20.…”

mentioning

confidence: 70%

Regioselective progesterone hydroxylation catalyzed by eleven rat hepatic cytochrome P-450 isozymes

Swinney¹,

Ryan²,

Thomas³

et al. 1987

Biochemistry

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Quantitative high-pressure liquid chromatographic assays were developed that separate progesterone and 17 authentic monohydroxylated derivatives. The assays were utilized to investigate the hydroxylation of progesterone by 11 purified rat hepatic cytochrome P-450 isozymes and 8 different rat hepatic microsomal preparations. In a reconstituted system, progesterone was most efficiently metabolized by cytochrome P-450h followed by P-450g and P-450b. Seven different monohydroxylated progesterone metabolites were identified. 16 alpha-Hydroxyprogesterone, formed by 8 of the 11 isozymes, was the only detectable metabolite formed by cytochromes P-450b and P-450e. 2 alpha-Hydroxyprogesterone was formed almost exclusively by cytochrome P-450h, and 6 alpha-hydroxyprogesterone and 7 alpha-hydroxyprogesterone were only formed by P-450a. 6 beta-hydroxylation of progesterone was catalyzed by four isozymes with cytochrome P-450g being the most efficient, and 15 alpha-hydroxyprogesterone was formed as a minor metabolite by cytochromes P-450g, P-450h, and P-450i. None of the isozymes catalyzed 17 alpha-hydroxylation of progesterone, and only cytochrome P-450k had detectable 21-hydroxylase activity. 16 alpha-Hydroxylation catalyzed by cytochrome P-450b was inhibited in the presence of dilauroylphosphatidylcholine (1.6-80 microM), while this phospholipid either stimulated (up to 3-fold) or had no effect on the metabolism of progesterone by the other purified isozymes. Results of microsomal metabolism in conjunction with antibody inhibition experiments indicated that cytochromes P-450a and P-450h were the sole 7 alpha- and 2 alpha-hydroxylases, respectively, and that P-450k or an immunochemically related isozyme contributed greater than 80% of the 21-hydroxylase activity observed in microsomes from phenobarbital-induced rats.

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Mass spectrometry of steroid systems–V

Cited by 46 publications

References 7 publications

Evidence for concerted kinetic oxidation of progesterone by purified rat hepatic cytochrome P-450g

Evidence for concerted kinetic oxidation of progesterone by purified rat hepatic cytochrome P-450g

Dislocations in deformed ZnSe single crystals as studied by Weak-beam electron microscopy

Regioselective progesterone hydroxylation catalyzed by eleven rat hepatic cytochrome P-450 isozymes

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