Kinetics of the D and I glycogen synthetase forms and their interconversion, in the sea scallop Pecten maximus.
In extracts from the adductor muscle of the shell-fish, Pecten maximus, glycogen synthetase (EC.2.4.1.11) was found. The enzyme occurs predominantly as D form (glucose-6-P dependent for activity). An I form (G-6-P independent) was also present. Kinetics of glycogen synthetase showed that the Ka for G-6-P in the D form was 10 fold higher than in the I form. Both forms of glycogen synthetase were interconverted through reactions catalyzed by phosphatase and kinase enzymes respectively. Glucose-6-P and Mg+2 must be present to stabilize glycogen synthetase and to activate the synthetase D phosphatase, found in the 90,000 X g protein-glycogen complex. The conversion of synthetase D to I was inhibited by F-, glycogen, ATP and UTP. When F- was present the effect of G-6-P on synthetase and phosphatase suggested that conversion involved the existence of more than a single glycogen synthetase phosphatase enzyme. ATP and Mg+2 were necessary for the conversion of synthetase I to D, and the conversion was stimulated by cAMP.
D000242:Cyclic AMP / Q000494:pharmacology; D005952:Glucose-6-Phosphatase / Q000032:analysis / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008974:Mollusca / Q000201:enzymology / Q000378:metabolism*; D014532:Uridine Diphosphate Glucose / Q000494:pharmacology
D000242:Cyclic AMP; D006006:Glycogen Synthase; D005952:Glucose-6-Phosphatase; D008274:Magnesium; D014532:Uridine Diphosphate Glucose