PMID: 36690Jan 1, 1979

Steroid specificity of human placental 5-ene-3 beta-hydroxysteroid oxidoreductase

Steroids
N Yoshida

Abstract

The properties of 5-ene-3 beta hydroxysteroid oxidoreductase (3 beta-HSD) from human placental homogenates were studied in vitro. The apparent Michaelis constants for 3 beta-HSD with the substrates pregnenolone (delta 5P) and dehydroepiandrosterone (DHA) were 170 nM and nM respectively. The optimal pH for both these substrates was between 10 and 12. With NAD as the substrate, the Km for the pregnenolone was 20 microM and for DHA, 17 microM. The activity of 3 beta-HSD was inhibited by various steroids. Competitive inhibitors (pregnenolone substrate) included: ethynylestradiol (inhibition constant Ki=7.3 nM), DHA (Ki=46 nM), estradiol-17 beta (Ki=46 nM), cholesterol (Ki=0.68 microM) and 16 alpha-hydroxydehydroepiandrosterone (16 alphaOHDHA) (Ki=2.2 microM). When the substrate was DHA, competitive inhibition occurred with the following steroids: ethynylestradiol (Ki=6.4 nM), estradiol-17 beta (Ki=69 nM), pregnenolone (Ki=91 nM), cholesterol (Ki=1.3 microM) and 16 alphaOHDHA (Ki=1.9 microM). 4-Ene-3-ketosteroids such as androstenedione, progesterone (delta 4P), norethindrone and chlormadinone acetate acted as noncompetitive inhibitors towards both substrates.

References

Jan 1, 1980·Journal of Steroid Biochemistry·M BedinL Cedard
Feb 1, 1982·Journal of Steroid Biochemistry·M A YounesP K Besch
Aug 1, 1983·Journal of Steroid Biochemistry·Y ChikhaouiA Crastes de Paulet
Jan 1, 1980·Pharmacology & Therapeutics·M R Juchau
Nov 9, 2000·The Journal of Steroid Biochemistry and Molecular Biology·A G PozziN R Ceballos

Citations

Sep 1, 1975·The Journal of Clinical Endocrinology and Metabolism·D F Fan, P Troen

Related Concepts

Norethindrone
Pregnenolone
Ketosteroids
Androstenedione Measurement
Hydroxysteroids
Ethinyl Estradiol
Progesterone
Placenta
NADH
Progesterone [EPC]

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