Drosophila melanogaster ma-l mutants are defective in the sulfuration of desulfo Mo hydroxylases.

Xanthine dehydrogenase was purified more than 1500-fold from crude extracts of wild type Drosophila melanogaster. Like the bovine milk and chicken liver enzymes, the purified Drosophila enzyme was inactivated by cyanide, and the cyanide-inactivated desulfo enzyme was reactivated by anaerobic incubation with 1 mM sulfide and 1 mM dithionite. Application of the resulfuration procedure to crude extracts of Drosophila ma-l flies which slow pleiotropic deficiencies of xanthine dehydrogenase, aldehyde oxidase, and pyridoxal oxidase led to the emergence of xanthine dehydrogenase and aldehyde oxidase activities. Representatives of all the five known complementation groups of ma-l mutants were amenable to activation; 59-95% of wild type xanthine dehydrogenase activity and 1-7% of wild type aldehyde oxidase activity were reconstituted. Evidence for the identity of in vitro reconstituted xanthine dehydrogenase from ma-l mutants with wild type enzyme is presented. Since the inactive xanthine dehydrogenase and aldehyde oxidase proteins present in ma-l mutants are identical with the catalytically inactive desulfo forms obtained by cyanide treatment of active enzymes, these data constitute evidence for genetic control of the incorporation of the cyanolyzable sulfur of Mo hydroxylases.