Direct measurement of in vivo flux differences between electrophoretic variants of G6PD from Drosophila melanogaster.
Demonstrating that naturally occurring enzyme polymorphisms significantly impact metabolic pathway flux is a fundamental step in examining the possible adaptive significance of such polymorphisms. In earlier studies of the glucose-6-phosphate dehydrogenase (G6PD) polymorphism in Drosophila melanogaster, we used two different methods, exploiting both genotype-dependent interactions with the 6Pgd locus, and conventional steady-state kinetics to examine activity differences between the two common allozymes. In this report we use 1-14C- and 6-14C-labeled glucose to estimate directly genotype-dependent flux differences through the pentose shunt. Our results show that G6pdA genotype possesses statistically lower pentose shunt flux than G6pdB at 25 degrees. We estimate this to be about a 32% reduction, which is consistent with the two former studies. These results reflect a significant responsiveness of pentose shunt flux to activity variation at the G6PD-catalyzed step, and predict that the G6PD allozymes generate a polymorphism for pentose shunt flux.
Labate
J
J
Department of Ecology and Evolution, State University of New York, Stony Brook 11794.
Eanes
W F
WF
D000818:Animals; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D014644:Genetic Variation; D005838:Genotype; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics*; D010427:Pentose Phosphate Pathway / Q000235:genetics*; D011110:Polymorphism, Genetic
D005954:Glucosephosphate Dehydrogenase