PMID: 818081Apr 10, 1976

Rabbit skeletal muscle glycogen synthase. I. Relationship between phosphorylation state and kinetic properties

The Journal of Biological Chemistry
P J RoachJ Larner


Nine samples of purified rabbit skeletal muscle glycogen synthase (UDP-glucose:glycogen 4-alpha-glucosyltransferase, EC were obtained with alkali-labile phosphate contents ranging from 0.27 to 3.49 residues per 85,000 molecular weight subunit. The enzyme samples appeared essentially homogeneous when analyzed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate and had relatively constant specific activity under standard conditions with saturating UDP-glucose and glucose-l-P concentrations (37.1 +/- 1.0 mumol of glucose incorporated/mg/min). When the UDP-glucose concentration was varied, deviations from Michaelis-Menten kinetics were observed for all samples (Hill slopes of 0.79 +/- 0.02), but these deviations were virtually abolished by the presence of 5 mM glucose-6-P. Glucose-6-P decreased the S0.5 (concentration required for half-maximal rate) for UDP-glucose. The plots of activity increase caused by glucose-6-P versus glucose-6-P concentration became progressively more sigmoid in shape with enzyme samples of higher phosphate content. Both the S0.5 for UDP-glucose and the M0.5 for glucose-6-P (concentration for half-maximal activation) were sensitive functions of the alkali-labile phospha...Continue Reading

Related Concepts

Sigmoid Colon
Protein Phosphorylation
Phosphate Measurement
Sodium Chloride, (24)NaCl
Sodium Dodecyl Sulfate
Polyacrylamide Gel Electrophoresis
Specimen Type - Skeletal Muscle

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