Author:
Chasiotis D.,Sahlin K.,Hultman E.
Abstract
The regulation of glycogenolysis in human muscle during isometric and dynamic exercise has been investigated. Total glycogen phosphorylase and synthase activities were unchanged during exercise. The fraction of phosphorylase in the alpha form at rest was estimated to be 20%, but the data indicate that the in vivo activity was low and critically dependent on the concentration of inorganic phosphate (Pi) in the muscle. Phosphorylase alpha increased initially 2.4-fold during isometric contraction and 1.6-fold during maximal bicycle exercise but reverted to or below the resting value at fatigue/exhaustion. At rest synthase I was 1713;48% of the total activity but decreased during exercise to about half of this value. The reciprocal changes in phosphorylase and synthase correlate with the enhanced rate of glycogenolysis during exercise. Michaelis constant (Km) for Pi was 27 mmol . l-1 for phosphorylase alpha and 7 mmol . l-1 for alpha + b. From consideration of the changes in Pi during exercise (to 20–30 mmol . l–1) it was concluded that Pi is one of the main factors determining phosphorylase activity and provides a link between phosphocreatine breakdown and glycogen utilization in muscle.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Cited by
140 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献