S-methyl-N,N-diethyldithiocarbamate (MeDDC) is an active metabolite in vivo of the alcohol deterrent disulfiram, but the enzymes responsible for its metabolism in humans are not known. We studied the role of both CYP450 and flavin monooxygenase (FMO) in human liver microsomes (HLM) in the metabolism of MeDDC. In HLM (pH 7.4) and in insect microsomes containing recombinant human FMO3 (pH 9.5, 0.05% TritonX-100), MeDDC sulfine was formed at a rate of 3.3±0.6 (n=11) and 11.3±0.5 (n=3) nmol/mg/min, respectively. Heating HLM at 45°C for 5 minutes (to inactivate FMO) caused 12% reduction in MeDDC sulfine formation. Likewise, 1 mM N-benzylimidazole (NBI, an inhibitor of CYP450) resulted in 93% decrease in product formation. O-Dealkylation of 7-ethoxycoumarin, a probe for CYP450, and sulfoxidation of methyl-p-tolyl sulfide, a probe for FMO, were reduced by 4% and 20% by heat inactivation and 100% and 82% by NBI, respectively. These data show that although MeDDC is an excellent substrate for FMO3, in HLM MeDDC sulfine is formed primarily by CYP450.
ASJC Scopus subject areas
- Pharmacology (medical)