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Predicate | Object |
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rdf:type | |
lifeskim:mentions | |
pubmed:issue |
2
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pubmed:dateCreated |
1983-6-10
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pubmed:abstractText |
The steady-state interaction between protein phosphatase-1 and its two inhibitor proteins was studied in vitro at low enzyme concentrations where the assumptions of the Michaelis-Menten equation appeared to be valid. Under these conditions, and in the absence of divalent cations, inhibitor-1 behaved as a mixed inhibitor using phosphorylase alpha as a substrate, whereas inhibitor-2 was a competitive inhibitor. The results demonstrate that inhibitor-1 and inhibitor-2 do not interact with protein phosphatase-1 in an identical manner. Inhibitor-1 was only a substrate for protein phosphatase-1 in the presence of Mn2+, and its dephosphorylation was inhibited competitively by inhibitor-2 (Kis = 8 nM). Inhibitor-1 did not inhibit its own dephosphorylation in the presence of Mn2+. Its Km as a substrate (190 nM) was very much higher than its Ki as an inhibitor (1.5-7.5 nM). The results are consistent with a model in which a single binding site for inhibitor-1 is present on protein phosphatase-1, distinct from the binding site for phosphorylase alpha. It is envisaged that the binding of inhibitor-1 to this site not only inhibits the dephosphorylation of other substrates but permits access of its phosphothreonine to the same catalytic group(s) responsible for the dephosphorylation of other substrates. G-substrate, a protein phosphorylated exclusively on threonine residues, did not inhibit the dephosphorylation of phosphorylase alpha and its dephosphorylation was potently inhibited by inhibitor-1 or inhibitor-2. The role of the phosphothreonine residue in inhibitor-1 is discussed in the light of these results.
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pubmed:language |
eng
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pubmed:journal | |
pubmed:citationSubset |
IM
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pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Carrier Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Enzyme Inhibitors,
http://linkedlifedata.com/resource/pubmed/chemical/Intracellular Signaling Peptides...,
http://linkedlifedata.com/resource/pubmed/chemical/Phosphoprotein Phosphatases,
http://linkedlifedata.com/resource/pubmed/chemical/Protein Phosphatase 1,
http://linkedlifedata.com/resource/pubmed/chemical/Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/protein phosphatase inhibitor-1,
http://linkedlifedata.com/resource/pubmed/chemical/protein phosphatase inhibitor-2
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pubmed:status |
MEDLINE
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pubmed:month |
May
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pubmed:issn |
0014-2956
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pubmed:author | |
pubmed:issnType |
Print
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pubmed:day |
2
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pubmed:volume |
132
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
309-13
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pubmed:dateRevised |
2008-11-21
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pubmed:meshHeading |
pubmed-meshheading:6301830-Carrier Proteins,
pubmed-meshheading:6301830-Chemical Phenomena,
pubmed-meshheading:6301830-Chemistry,
pubmed-meshheading:6301830-Enzyme Inhibitors,
pubmed-meshheading:6301830-Intracellular Signaling Peptides and Proteins,
pubmed-meshheading:6301830-Kinetics,
pubmed-meshheading:6301830-Phosphoprotein Phosphatases,
pubmed-meshheading:6301830-Protein Phosphatase 1,
pubmed-meshheading:6301830-Proteins,
pubmed-meshheading:6301830-Substrate Specificity
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pubmed:year |
1983
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pubmed:articleTitle |
A kinetic analysis of the effects of inhibitor-1 and inhibitor-2 on the activity of protein phosphatase-1.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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