Developmental control of α-1–4 glucan phosphorylase in the cellular slime mold Dictyostelium discoideum

Glycogen phosphorylase activity in cells of Dictyostelium discoideum appears to be developmentally regulated, and experiments with actinomycin D and cycloheximide suggest that both the appearance and disappearance require prior RNA and concomitant protein synthesis.

Abstract

Glycogen phosphorylase activity is undetectable in vegetative, multiplying cells of wild type and mutant strains of Dictyostelium discoideum but appears during development. The specific activity of this enzyme is undetectable in developing cells until mid-aggregation and reaches a maximum at mid-culmination. Thereafter the enzyme activity begins to decrease and eventually disappears. Appropriate experiments with actinomycin D and cycloheximide suggest that both the appearance and disappearance of glycogen phosphorylase require prior RNA and concomitant protein synthesis. The activity of this enzyme in cells of Dictyostelium discoideum appears therefore to be developmentally regulated. Further studies with mutants of D. discoideum support this view. The enzyme was purified 100-fold from crude extracts and its properties were examined. These results are discussed in the light of what is known about the regulation of polysaccharide metabolism during culmination.