Aldehyde Oxidase and Xanthine Dehydrogenase from Wild‐Type Drosophila melanogaster and Immunologically Cross‐Reacting Material from ma‐1 Mutants

Abstract

The pleiotropic effect of the ma-1 mutation on the enzymes xanthine dehydrogenase and aldèhyde oxidase in Drosophila melanogaster can most readily be explained by assuming that the enzymes share a subunit or cofactor whose synthesis is controlled by the ma-1 locus. According to this hypothesis a protein or a tightly bound cofactor common to both enzymes should be inactive or missing in the corresponding immunologically cross-reacting material found in ma-1 flies. Three of the proteins involved were purified by immunoadsorption: xanthine dehydrogenase, xanthine dehydrogenase cross-reacting material and aldehyde oxidase. On gel filtration xanthine dehydrogenase and xanthine dehydrogenase cross-reacting material showed identical molecular weights of 300000 whereas 280000 was found for aldehyde oxidase. All three proteins appear to be dimers. Under dissociating conditions (polyacrylamide electrophoresis in the presence of sodium dodecyl sulfate) a single protein band with a mobility corresponding to one half the native molecular weight was found. There was no evidence of small polypeptide subunits. All three proteins contain FAD, molybdenum and iron, cofactors known to be present in related vertebrate enzymes. Thus the ma-1 locus apparently does not control the mere incorporation of a polypeptide subunit or one of the prosthetic groups necessary for activity into the enzymes.