11β-Hydroxysteroid dehydrogenase activity in progesterone biotransformation by the filamentous fungus Cochliobolus lunatus

Progesterone biotransformation was examined in relation to hydroxylating and dehydrogenating enzymes of Cochliobolus lunatus. 11β-hydroxysteroid dehydrogenase activity (11β-HSD) was located in cytosolic fraction and was NADP-dependent, inducible by progesterone and apparently unidirectional. Several inhibitors of 11β-hydroxysteroid dehydrogenase were tested; furosemide, glycyrrhizic-acid and carbenoxolone did not influence the dehydrogenation of 11β-hydroxy-4-pregnene-3,20-dione to 4-pregnene-3,11,20-trione, although grapefruit juice significantly reduced the rate of progesterone hydroxylation.