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H Inano

Publications and source records attributed to H Inano.

At least 91 records · Page 5Linked to original sources
PubMed1978

In vitro effect of 16alpha-hydroxyprogesterone on the enzyme activities related to androgen production in human testes.

Progesterone was converted in vitro to 16alpha- and 17alpha-hydroxyprogesterones in the presence of NADPH by the testicular microsomal fraction (precipitate at 10 000 x g-105 000 x g) obtained from patients with prostatic carcinoma. 16alpha-Hydroxyprogesterone was not metabolized by either the microsomal or the cytosol fractions, and accumulated in the incubation medium. 16alpha-Hydroxyprogesterone competitively inhibited the activity of the C-17-C-20 lyase in the testicular microsomal fraction with an estimated inhibitor constant of 72 micron. Moreover, the 16alpha-hydroxyprogesterone non-competitively inhibited the activity of the 20alpha-hydroxysteroid dehydrogenase in the testicular cytosol fraction and had an estimated inhibitor constant of 52.9 micron. Other testicular enzymes related to steroid metabolism, such as delta5-3beta-hydroxysteroid dehydrogenase coupled with the delta4-delta5 isomerase, 16alpha-hydroxylase, 17alpha-hydroxylase, and 17beta-hydroxysteroid dehydrogenase were not influenced in vitro by 16alpha-hydroxyprogesterone at the concentration of 0.1 mM. From these findings, it is concluded that 16alpha-hydroxyprogesterone inhibit specifically the cleavage of the side-chain of 17alpha-hydroxypregnenes in the course of androgen formation from pregnenolone in vitro.

Androgens↗
PubMed1975

Relationship between steroids and pyridine nucleotides in the oxido-reduction catalyzed by the 17 beta-hydroxysteroid dehydrogenase purified from the porcine testicular microsomal fraction.

The 17 beta-hydroxysteroid dehydrogenase which was purified from porcine testicular microsomal fraction [Inano, H. and Tamaoki, B (1974) Eur. J. Biochem. 44, 13-23] catalyzed the reduction of androstenedione to testosterone with the accompanying oxidation of equimolar NADPH. For the oxido-reduction of the steroids, the 17 beta-hydroxysteroid dehydrogenase preferred NADP(H) to NAD(h). Transhydrogenation from NADPH to NAD+ or NADH to NADP+ through the cyclic oxido-reduction of the steroids by the purified 17 beta hydroxysteroid dehydrogenase preparation was not spectrophotometrically detectable, because of selective preference of the testicular 17 beta-hydroxysteroid dehydrogenase against NADP(H). To examine stereospecific transfer of the hydrogen from NADPH to androstenedione by the purified 17 beta-hydroxysteroid dehydrogenase, the following tritiated cofactors were synthesized: [4-3-H]NADP+ was prepared by catalytic replacement from non-radioactive NADP+ and 3H2O in the presence of potassium cyanide. Then, [4-pro-R3H]NADPH was enzymatically synthesized from the [4-3H]NADP+ by glucose 6-phosphate and its dehydrogenase. On the other hand, [4-pro-S-3H]NADPH was prepared from the [4-3H]NADP+ by isocitrate and isocitrate dehydrogenase. When androstenedione was incubated with the 17 beta-hydroxysteroid dehydrogenase in the presence of these stereospecifically 3H-labeled cofactors, only the tritium located at 4-pro-S position of the nicotinamide moiety of NADPH was transferred to testosterone. The location of the tritium in the testosterone molecule produced, 17alpha-position of the steroid, was assigned by the fact that the tritium of the testosterone remained in its molecule after acetylation, but was completely lost by oxidation.

Androstenedione↗