Identification and partial characterization of bovine heart cytosolic phosphorylase phosphatases.
The properties of phosphatases in bovine heart cytosol were studied. Two isozymic forms of protein phosphatase H (H-1 and H-2) were resolved by chromatography on DEAE-Sephacel. The two isoenzymes had identical physical properties (Mr 260,000, 7.9 S). Treatment with 80% ethanol activated both isozymes and converted H-1 to a Mr 35,500 form and H-2 to Mr 67,000 and Mr 35,500 forms. Both H-1 and H-2 and their lower Mr activated forms had essentially identical Km values for phosphorylase a. The heart cytosol also contained a latent phosphatase (Fc) which could be activated by preincubation with either ATP X Mg and an activating factor (FA), or by Mn/trypsin treatment. The latter procedure converted the latent Fc (Mr 200,000) to a Mn2+-independent Mr 34,500 form. Both activated forms of Fc had similar Km values which were fourfold lower than the affinity of the protein phosphatase H forms for the phosphorylase a substrate.
Dickey-Dunkirk
S
S
Mardaus
M C
MC
Killilea
S D
SD
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D008345:Manganese / Q000378:metabolism; D008970:Molecular Weight; D009206:Myocardium / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010765:Phosphorylase Phosphatase / Q000378:metabolism*
D007527:Isoenzymes; D008345:Manganese; D000255:Adenosine Triphosphate; D010749:Phosphoprotein Phosphatases; D010765:Phosphorylase Phosphatase; D008274:Magnesium