AGI, a previously unreported D. melanogaster alpha-glucosidase: partial purification, characterization, and cytogenetic mapping.

Inbred Drosophila melanogaster stocks were surveyed for alpha-glucosidases with nondenaturing gel electrophoresis using a fluorogenic substrate to stain the gels. The glucosidase most active under these conditions is polymorphic. We established that the polymorphism is genetic in origin and that the glucosidase was not likely to be a previously characterized enzyme. The gene encoding the enzyme was mapped cytogenetically to 33 A1-2- 33A8-B1, confirming that this is an enzyme not yet reported in D. melanogaster. The enzyme was partially purified by elution from nondenaturing gels, which enabled us to establish that it has optimal activity at pH 6 and interacts most strongly with alpha-1-4 glucosides. A developmental and tissue survey suggested that this enzyme could have a purely digestive role or be involved in carbohydrate metabolism inside the organism. We propose that this enzyme is involved in either starch digestion or glycogen metabolism.