The isolation and characterization of mutant alleles at a new X-linked locus, mex, affecting NADP(+)-dependent enzymes in Drosophila melanogaster.

The isolation and characterization of mutant alleles in a regulatory gene affecting NADP(+)-dependent enzymes are described. The locus, mex, is at position 26.5 +/- 0.74 on the X chromosome of Drosophila melanogaster. The newly isolated mutant allele, mex1, is recessive to either the mex allele found in Oregon-R wild-type individuals or that found in the cm v parental stock in which the new mutants were induced. The mex1 mutant allele is associated with statistically significant decreases in malic enzyme (ME) specific activity and ME specific immunologically cross-reacting material (ME-CRM) in newly emerged adult males. During this same developmental stage in males, the NADP(+)-dependent isocitrate dehydrogenase specific activity increases to statistically significant levels. Females of the mex1 mutant strain show statistically significant elevated levels of the pentose phosphate shunt enzymes, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Isoelectric focusing and thermolability comparisons of the active ME from mutant and control organisms indicate that the enzyme is the same. Developmental profiles of mex1 and control strains indicate that this mutant allele differentially modulates the levels of ME enzymatic activity and ME-CRM during development.