OXIDATION OF DIMETHYLSELENIDE TO DIMETHYLSELENOXIDE BY MICROSOMES FROM RAT-LIVER AND LUNG AND BY FLAVIN-CONTAINING MONOOXYGENASE FROM PIG-LIVER

Oxidation of [Se-75]dimethylselenide by rat liver and lung microsomes and by purified flavin-containing monooxygenase from pig liver was dem onstrated. Quantitation of the nonvolatile product showed a 1:1 stoich iometry with NADPH oxidation, consistent with selenoxide formation. Th e apparent K-m for dimethylselenide was 0.7 mu M with rat liver micros omes and 0.3 mu M with purified pig liver enzyme. Facile reversal of d imethylselenide oxidation by reducing agents present in microsomes, an d by glutathione, indicates that redox cycling can occur. Unlabeled di methylselenoxide carrier circumvented reduction of the labeled product , permitting quantitation. This is the First demonstration of a natura lly occurring selenium substrate for the microsomal flavin-containing monooxygenase. (C) 1994 Academic Press, Inc.