M-GLYCOGENIN, THE PROTEIN MOIETY OF NEUROSPORA-CRASSA PROTEOGLYCOGEN,IS AN AUTOGLUCOSYLATING AND TRANSGLUCOSYLATING ENZYME

Neurospora crassa proteoglycogen was purified and its protein moiety, M-glycogenin, was released by amylolytic treatment. The released prote in was capable of autoglucosylation from UDP-glucose forming glucosyl- alpha 1,4-glucosyl linkage. The kinetics of autoglucosylation suggeste d an intramolecular mechanism of reaction. M-glycogenin was also able to glucosylate dodecyl-beta-maltoside and autoglucosylate, simultaneou sly and independently. Both auto- and transglucosylation reactions wer e dependent on Mn2+. Thus, M-glycogenin, which has also been described as the constituent of Escherichia coli proteoglycogen (A. Goldraij an d J. A. Curtino, 1993, Biochem. Mel. Biol. Int. 30, 453-458), is a glu cosyltransferase that bears similar catalytic properties with mammalia n glycogenin. This is the first report on the enzymatic character of t he protein constituent of proteoglycogen in primitive organisms, which suggest that the mechanism for the de novo biosynthesis of glycogen w as conserved over a very long period of evolution. (C) 1996 Academic P ress, Inc.