Glycogen synthase a was purified over 500-fold by a procedure which involved solubilisation of the enzyme from a protein-glycogen complex by the action of endogenous phosphorylase and debranching enzyme, followed by DEAE-cellulose chromatography, and either gel filtration on Sepharose 4B or fractionation with polyethylene glycol. 15 tng of protein could be obtained from 1000 g of muscle in five days, corresponding to a yield of 20%. The purity was over 90% as judged by gel electrophoresis and ultracentrifugal analysis. The amino acid composition was determined and the absorption coefficient, A1%280nm, measured refractometrically was 13.4.
Glycogen synthase a sedimented as two major components, both of which were enzymatically active. The smaller species (13.3S) comprised 85% and the larger species (19.0S) 15% of the material. The molecular weight of the 13.3-S component was determined to be 377000 by high-speed sedimentation equilibrium centrifugation. The subunit molecular weight measured by gel electrophoresis in the presence of sodium dodecylsulphate was 88000 indicating that the 13.3-S species is a tetramer.
The properties of the enzyme are compared to those obtained by other workers.
- Cyclic AMP
adenosine cyclic 3′: 5′-monophosphate
Glycogen synthase (EC 126.96.36.199)
protein kinase or ATP: protein phosphotransferase (EC 188.8.131.52)
glycogen synthase phosphatase (EC 3.1.3.-)
phosphorylase kinase or ATP: phosphorylasc phosphotransferase (EC 184.108.40.206): phosphorylase (EC 220.127.116.11): debranching enzyme or amylo-1,6-glucosidase (EC 18.104.22.168): β galactosidase (EC 22.214.171.124)