The inducible and cytochrome P450-containing dehydroepiandrosterone 7alpha-hydroxylating enzyme system of Fusarium moniliforme.

ABSTRACT

7Alpha-hydroxylation of DHEA by Fusarium moniliforme was investigated with regard to inducibility and characterization of the responsible enzyme system. Using GC/MS, the 7-hydroxylated metabolites of DHEA produced after biotransformation by Fusarium moniliforme mycelia were identified. The strain of Fusarium moniliforme hydroxylated DHEA predominantly at the 7alpha-position, with minor hydroxylation occurring at the 7beta-position. Constitutive 7alpha-hydroxylation activity was low, but DHEA induced the enzyme complex responsible for 7alpha-hydroxylation via an increase in protein synthesis. DHEA 7alpha-hydroxylase was found to be mainly microsomal, and the best production yields of 7alpha-hydroxy-DHEA (28.5 +/- 3.51 pmol/min/mg protein) were obtained with microsomes prepared from 18-h-induced mycelia. Kinetic parameters (KM=1.18 +/- 0.035 microM and Vmax=909 +/- 27 pmol/min/mg protein) were determined. Carbon monoxide inhibited 7alpha-hydroxylation of DHEA by microsomes of Fusarium moniliforme. Also, exposure of mycelia to DHEA increased microsomal P450 content. These results demonstrated that (i) DHEA is 7alpha-hydroxylated by microsomes of Fusarium moniliforme; (ii) DHEA induces Fusarium moniliforme 7alpha-hydroxylase; (iii) this enzyme complex contains a cytochrome P450.