Structural and functional characterization of the Drosophila glycogen phosphorylase gene

We identified a P element insertional mutant of the Drosophila glycogen phosphorylase (DGPH) gene. Glycogen phosphorylase protein concentration and enzyme activity are decreased while glycogen content is increased in flies homozygous for the mutant allele. The DGPH gene has been cloned and sequenced; its open reading frame codes for a protein of 844 amino acids with a predicted molecular mass of 97 kDa. Comparison of the conceptual amino acid sequence of the Drosophila glycogen phosphorylase with glycogen phosphorylase sequences from other organisms shows a high degree of homology to mammalian enzymes. All the residues of the allosteric effector binding sites, the active site, and the site of phosphorylation are exactly conserved, but some of the residues of the glycogen storage site are not.