The Protein Phosphatases Involved in Cellular Regulation. 6. Measurement of Type-1 and Type-2 Protein Phosphatases in Extracts of Mammalian Tissues; an Assessment of Their Physiological Roles

作者：Thomas S. Ingebritsen, Alexander A. Stewart, Philip Cohen · 发表于：European Journal of Biochemistry · 年份：1983 · DOI：10.1111/j.1432-1033.1983.tb07362.x · 被引用次数：363 · 研究领域：Glycogen Storage Diseases and Myoclonus、Mitochondrial Function and Pathology、Alkaline Phosphatase Research Studies

Methods were developed for quantifying protein phosphatases-1, 2A, 2B and 2C in cell extracts, and these procedures were exploited to determine their tissue and subcellular distributions. In addition, the contribution of each enzyme to the total protein phosphatase activity in skeletal muscle and liver extracts towards nine proteins involved in the control of glycogen metabolism, glycolysis/gluconeogenesis, fatty acid synthesis and cholesterol synthesis was assessed. Each protein phosphatase was present at significant concentrations in skeletal muscle, heart muscle, liver, brain and adipose tissue, although the relative amounts differed considerably. In skeletal muscle, protein phosphatase-1 was the major enzyme acting on phosphorylase, glycogen synthase and phosphorylase kinase (beta-subunit), and thus was the major protein phosphatase responsible for the inactivation of glycogenolysis and stimulation of glycogen synthesis. This idea was reinforced by the observation that 50% of the protein phosphatase-1 activity was associated with the protein-glycogen complex. In the liver, protein phosphatases-1, 2A and 2C each appear to play a role in the regulation of glycogen metabolism. Protein phosphatase-1 accounted for a significant fraction of the total potential activity towards phosphorylase and glycogen synthase, and was the major phosphorylase kinase (beta-subunit) phosphatase of this tissue. In addition, it was the only protein phosphatase present in the protein-glycogen comp...