P450 catalysed S-oxidation of dibenzothiophene by Cunninghamella elegans

1. Approximately 98% of dibenzothiophene (DBT) was converted to DBT sulphoxide (86% of total metabolites) and DBT sulphone (14% of total metabolites) after a 24-h incubation with the filamentous fungus Cunninghamella elegans (ATCC-36112). 2. DBT sulphoxidation was significantly decreased in incubations with the concomitant additions of metyrapone, piperonyl butoxide and 1-aminobenzotriazole indicating a P450 monooxygenase-catalysed reaction. 3. DBT sulphoxidation was also significantly decreased by methimazole, but only slightly decreased with a thiourea addition, suggesting a possible role of a flavin-containing, monooxygenase-catalysed activity. 4. The extracellular filtrate of C. elegans failed to show measurable DBT oxidation, showing that biotransformation is intracellular and is not catalysed by an extracellular process.