The isolation and characterization of a mutant allele at a new X-linked locus,mex, affecting NADP+-dependent enzymes inDrosophila melanogaster

Abstract

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.

Natural and Synthetic Alleles Provide Complementary Insights Into the Nature of Selection Acting on theMenPolymorphism ofDrosophila melanogaster

“…The final decrease in IDH activity with the Men complete knockout does not fit a model of activity compensation, but is consistent with some earlier observations of the interaction across large-scale differences in activity between these loci in larvae Bentley et al 1983;Geer and Laurie-Ahlberg 1984). Gromnicki and Bentley (1991), however, found compensatory changes in activity between these enzymes. The interaction between IDH and MEN is apparently complex, at least over large-scale changes in activity.…”

Dipeptidase-C inDrosophila melanogaster: Genetic, ontogenetic, and tissue-specific variation

“…Activities are often intercorrelated among enzymes that are functionally related (i.e., share the same substrate or product) or participate in the same metabolic pathway (Clark, 1989;Wilton et al, 1982). The coordinate expression of molybdenum hydroxylases such as xanthine dehydrogenase, sulfite oxidase, and aldehyde oxidase is affected by modifier loci (Baker, 1973;Bentley et al, 1981;Williamson, 1979, 1982;Finnerty, 1976), and the coordinate regulation of some NADP(+)-dependent enzymes has been shown to be modulated developmentally by mex, an X-linked regulatory gene (Gromnicki and Bentley, 1991). Activities of glucose-6-phosphate and 6-phosphogluconate dehydrogenases (G6PD and 6PGD, respectively), two enzymes involved in the pentose phosphate shunt, are significantly correlated throughout the developmental stages of Drosophila melanogaster .…”

Chromosomal effects on peptidase activities inDrosophila melanogaster

“…Unlinked activity modifiers in Drosophila melanogaster often affect the concentration of enzymes, and such observations have been well documented for alcohol dehydrogenase, sn-glycerol-3-phosphate dehydrogenase, and glucose-6-phosphate and 6-phosphogluconate dehydrogenases (Laurie-Ahlberg, 1985). An interesting example is rnex, an X-linked regulatory gene involved in the coordinate regulation of some NADP(+)-dependent enzymes (Gromnicki and Bentley, 1991). The basis for the variation in Kin, Vma~, and specific activity of LAP P between Hochi-R and NC25 III requires further investigation.…”

“…The Drosophila genome, for example, is characterized by an abundance of genetic modifiers that affect activity levels of enzymes without altering the primary structure of these molecules at the time of translation (for review see Laurie-Ahlberg, 1985). Yet few examples exist of activity modifiers that exert their effects pleiotropically on metabolically related enzymes or proteins Williamson, 1979, 1982;Gromnicki and Bentley, 1991;Wilton et al, 1982). One approach to assessing pleiotropic effects of modifiers on enzyme activity variation in natural populations is to study genetic effects on the expression of enzymes with similar biochemical or physiological functions, such as the peptidases in…”