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Native cytosolic protein phosphatase‐1 (PP‐1S) containing modulator (inhibitor‐2) is an active enzyme
Author(s) -
Bollen Mathieu,
DePaoli-Roach Anna A.,
Stalmans Willy
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00391-2
Subject(s) - phosphatase , chemistry , phosphorylation , protein subunit , cytosol , enzyme , biochemistry , protein kinase a , enzyme activator , microbiology and biotechnology , biology , gene
In vitro, the modulator protein (inhibitor‐2) slowly converts the catalytic subunit of protein phosphatase‐1 (PP‐1 c ) into an inactive ‘MgATP‐dependent form’ that can be reactivated by the transient phosphorylation of modulator with GSK‐3/F A . We report here that this modulator‐induced inactivation of PP‐1 C can be blocked by addition (at pH 7.5) of either 0.3 mM NaF or 150 mM NaCl, or by raising the pH to 8.5. Making use of a combination of the latter conditions, we have partially purified a soluble modulator‐associated form of PP‐1 (PP‐1S) from rabbit skeletal muscle as a spontaneously active enzyme that cannot be further activated by kinase GSK‐3/F A . These observations argue against a role for the ‘MgATP‐dependent’ form of PP‐1S as an inactive reservoir of PP‐1 C . PP‐1S was separated on aminohexyl Sepharose from another active, cytosolic species of PP‐1, which appears to be a proteolytic product of the glycogen‐bound PP‐1G.