1. Kinetics of the D and I glycogen synthetase forms and their interconversion, in the sea scallop Pecten maximus.
- Author
-
Vázquez-Baanante I and Rosell-Pérez M
- Subjects
- Cyclic AMP pharmacology, Glucose-6-Phosphatase analysis, Glucose-6-Phosphatase metabolism, Magnesium pharmacology, Mollusca enzymology, Uridine Diphosphate Glucose pharmacology, Glycogen Synthase metabolism, Mollusca metabolism
- Abstract
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.
- Published
- 1979