The Purification and Properties of Rabbit Skeletal Muscle Glycogen Synthase

Authors


Abstract

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.

Abbreviations
Cyclic AMP

adenosine cyclic 3′: 5′-monophosphate

glucose-6-P

glucose 6-phosphate

Enzymes
 

Glycogen synthase (EC 2.4.1.11)

 

protein kinase or ATP: protein phosphotransferase (EC 2.7.1.37)

 

glycogen synthase phosphatase (EC 3.1.3.-)

 

phosphorylase kinase or ATP: phosphorylasc phosphotransferase (EC 2.7.1.38): phosphorylase (EC 2.4.1.1): debranching enzyme or amylo-1,6-glucosidase (EC 3.2.1.33): β galactosidase (EC 3.2.1.23)

Ancillary