A third locus (ipo) affecting pyridoxal oxidase in Drosophila melanogaster.

X A N T H I N E dehydrogenase (XDH) o€ Drosophila melamgaster is controlled by at least three loci. Electrophoretic evidence (YEN and GLASSMAN 1965) indicates that r y (rosy eye color, 3-52.4), a mutant that lacks XDH (GLASSMAN and MITCHELL 1959), is the structural gene for this enzyme. Mutants of the other two loci, ma-1 (maroon-like eye color, 1-64?) and lxd (low xanthine dehydrogenase, 3-33?), have 0 and 25% normal XDH activity, respectively (GLASSMAN and MITCHELL 1959; KELLER and GLASSMAN 1964), and are also deficient in pyridoxal oxidase (FORREST, HANLY and LAGOWSKI 1961 ; GLASSMAN et al., 1964), and aldehyde oxidase (COURTRIGHT 1967). Table 3, below, shows the distribution of the enzyme activities in the various mutants. Other properties of this enzyme system have been summarized in a review by GLASSMAN (1965). By assaying many strains, a new mutant lpo (low pyridoxal oxidase) has been found which affects only pyridoxal oxidase and may be a structural gene for pyridoxal oxidase. Some of these data have appeared elsewhere in preliminary form ( GLASSMAN et al. 1968).