Enzymes of glycogen mobilization in the photosynthetic procaryote, Anacystis nidulans

Glycogen, the principal storage compound of assimilatory products in Anacystis nidulans, is synthesized in the light and degraded in the dark. (14)C-labelled glycogen and its radioactive limit dextrin obtained by phosphorylase action were used as substrates to identify enzymes involved in glycogen mobilization. A crude homogenate of cells kept in the dark contained the following enzymes: glycogen phosphorylase (EC 2.4.1.1.) that is firmly bound to glycogen, a debranching enzyme that hydrolyzes 1,6-α-glucosidic bonds, and an α-glucosidase (EC 3.2.1.20). Other amylolytic enzymes were not detectable Using ion exchange chromatography on DEAE-cellulose, α-glucosidase and the debranching enzyme could be partly separated from each other and completely from the phosphorylase-glycogen complex. On the basis of their known substrate specificities, the cooperation of these 3 enzymes is sufficient to account for the complete conversion of glycogen into glucose and glucose 1-phosphate.