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  • Title: Identification and partial characterization of bovine heart cytosolic phosphorylase phosphatases.
    Author: Dickey-Dunkirk S, Mardaus MC, Killilea SD.
    Journal: Arch Biochem Biophys; 1985 Aug 15; 241(1):232-42. PubMed ID: 2992391.
    Abstract:
    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.
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