title: The myosin-bound form of protein phosphatase 1 (PP-1M) is the enzyme that dephosphorylates native myosin in skeletal and cardiac muscles.
abstract: The myosin-bound form of protein phosphatase 1 (PP-1M) and the glycogen-bound form (PP-1G) together account for virtually all the phosphatase activity in rabbit skeletal muscle extracts towards native myosin. PP-1M has a 3-fold higher activity towards native myosin than does PP-1G and accounts for at least 60% of the myosin phosphatase activity in rabbit skeletal muscle. PP-1M accounts for 90% of the myosin phosphatase activity in bovine cardiac muscle, where PP-1G is essentially absent. The high activity of PP-1M towards native myosin appears to arise from interaction of the catalytic subunit with the putative myosin-binding subunit, since chymotryptic digestion liberates a catalytic subunit having the same characteristics as that released by limited proteolysis of PP-1G. Protein phosphatase 2A in skeletal and cardiac muscles is very active towards the isolated myosin P-light chain, but ineffective in dephosphorylating native myosin. The results suggest that PP-1M is the enzyme that dephosphorylates myosin in skeletal and cardiac muscle.
authors.affiliation: Department of Biochemistry, Medical Sciences Institute, The University, Dundee, UK.
authors.forename: A A
authors.initials: AA
authors.lastname: Chisholm
authors.forename: P
authors.initials: P
authors.lastname: Cohen
mesh_terms: D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism; D004492:Edetic Acid; D006003:Glycogen / Q000378:metabolism; D007163:Immunosorbent Techniques; D009132:Muscles / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D017830:Octoxynol; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011092:Polyethylene Glycols; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D011817:Rabbits; D014357:Trypsin / Q000378:metabolism
chemical_list: D011092:Polyethylene Glycols; D017830:Octoxynol; D006003:Glycogen; D004492:Edetic Acid; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D002918:Chymotrypsin; D014357:Trypsin; D009218:Myosins