An electrophoretic and biochemical comparison of soluble trehalase from Drosophila melanogaster and D. simulans

Soluble trehalases isolated from adult Drosophila melanogaster and D. simulans can be distinguished following polyacrylamide gel electrophoresis in triethanolamine gels. Ferguson plots indicated that the two forms are related as charge isomers. This suggests that these trehalases are most likely allozymes, an interpretation which is consistent with the taxonomic relationship of the two species. A comparison of the pH optima and K_m of the soluble enzyme obtained from 0 to 3-day-old and 12 to 15-day-old D. melanogaster and 0 to 4-day-old and 12 to 15-day-old D. simulans revealed no differences. The pH optima of the enzymes lay between 5.5 and 6.0 and the average K_m, estimated from Lineweaver-Burk plots, is 7.26 × 10⁺⁴ M. However, there were marked differences in the maximal catalytic activity per gram wet weight of soluble trehalases; the catalytic activity of both age samples of D. simulans enzyme exceeded that of both samples from D. melanogaster. In both species, the younger flies showed higher activity.