Reversibility of Steroid -Isomerase

II. THE REACTION SEQUENCE IN THE CONVERSION OF ANDROST-4-ENE-3,17-DIONE TO 3-HY-DROXYANDROST-5-EN-17-ONE BY SHEEP ADRENAL MICROSOMES

From the ¹ From the John Collins Warren Laboratories of the Huntington Memorial Hospital of Harvard University, at the Massachusetts General Hospital, and the Department of Biological Chemistry, Harvard Medical School, Boston, Massachusetts 02114

When large quantities of androst-4-ene-3,17-dione were incubated with reduced diphosphopyridine nucleotide and an acetone powder of sheep adrenal microsomes, 3ß-hydroxyandrost-4-en-17-one and its ⁵ isomer were isolated and crystallized as their benzoates. The melting points and infrared spectra were in agreement with those of the corresponding standards. A similar incubation of unlabeled androst-5-ene-3,17-dione produced 3ß-hydroxyandrost-5-en-17-one in good yield. Since incubation of 3ß-hydroxyandrost-4-en-17-one-3-³H yielded nonradioactive 3ß-hydroxyandrost-5-en-17-one and androst-4-ene-3,17-dione, it was concluded that the isomerase did not act on the allylic alcohol.

3ß-Hydroxyandrost-4-en-17-one-3-³H and -3-H were incubated simultaneously in the presence of diphosphopyridine nucleotide and an acetone powder of sheep adrenal microsomes for varying times. There was no measurable difference in the rates of oxidation of these two allylic alcohols.

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