Glycogen synthesis in the fungus Neurospora crassa

An enzymic activity, obtained from Neurospora crassa, catalyzing the incorporation of ¹⁴C]glucose from ADP-¹⁴C]glucose into a glucan of the glycogen type, is described. The properties of the ADPglucose: glycogen glucosyltransferase as compared with those of the already known UDP glucose: glycogen glucosyltransferase were studied. The radioactive products obtained with UDP-¹⁴C]glucose or ADP-¹⁴C]glucose released all the radioactivity as maltose after α or β amylase treatment. Glucose 6-phosphate stimulated the synthetase when UDP-¹⁴C]glucose was the substrate but the stimulation was much greater with ADP-¹⁴C]glucose as glucosyl donor. Glucose 6-phosphate plus EGTA gave maximal stimulation. The system was completely dependent on the presence of a ‘primer’ of the α 1 → 4 glucan type.