METYRAPONE REDUCTASE PURIFIED PARTIALLY FROM LIVER-MICROSOMES OF MALE-RATS - THE ENZYME DIFFERS FORM ACETOHEXAMIDE REDUCTASE

An enzyme catalyzing the reduction of metyrapone, a diagnostic drug wi th a ketone group, was partially purified from liver microsomes of mal e rats. The partially purified metyrapone reductase had no ability to reduce acetohexamide, an oral antidiabetic drug with a ketone group, e ven though both metyrapone and acetohexamide are reduced in Liver micr osomes of male rats. These results clearly indicate that the reduction of these two drugs can be catalyzed by different enzymes. The partial ly purified metyrapone reductase was found to reduce aldehydes, ketone s and menadione. The substrate specificities were in fair agreement wi th those of carbonyl reductase. However, the partially purified enzyme was strongly inhibited by inhibitors of aldehyde reductase, such as b arbital, phenobarbital and sodium valproate.