title: Latent forms of type-1 protein phosphatase in rabbit skeletal muscle.
abstract: We have examined the characteristics of partially purified forms of rabbit skeletal muscle type-1 protein phosphatase (PP-1). Over 90% of PP-1 in unfractionated extracts and in glycogen particles was inactive, but could be activated by the divalent cations, Mn2+ or Co2+ (Me2+) plus trypsin. Gel filtration of muscle extracts revealed two inactive forms of PP-1; one activated by Me2+ alone or Me2+ plus trypsin, and a second containing inhibitor-2 and activated only by Me2+ plus trypsin. The kinetics of Me2+ plus trypsin activation revealed that after DEAE-chromatography, PP-1 was altered from the forms in crude extracts, gel filtered extracts or glycogen particles. The results indicate that the purified form of PP-1 catalytic subunit has properties which distinguish it from the forms of the enzyme in muscle extracts.
authors.affiliation: Division of Biology and Medicine, Brown University, Providence, RI 02912.
authors.forename: P A
authors.initials: PA
authors.lastname: Gruppuso
authors.forename: C L
authors.initials: CL
authors.lastname: Shriner
authors.forename: D L
authors.initials: DL
authors.lastname: Brautigan
mesh_terms: D000818:Animals; D000937:Antigen-Antibody Reactions; D002413:Cations, Divalent; D002850:Chromatography, Gel; D004789:Enzyme Activation; D009132:Muscles / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D010765:Phosphorylase Phosphatase / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism*; D011817:Rabbits; D014357:Trypsin / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D010749:Phosphoprotein Phosphatases; D010765:Phosphorylase Phosphatase; D014357:Trypsin