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      Phosphorylation of the multicatalytic proteinase complex from bovine pituitaries by a copurifying cAMP-dependent protein kinase

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      Archives of Biochemistry and Biophysics
      Elsevier BV

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          Abstract

          The multicatalytic proteinase complex (MPC) constitutes a major nonlysosomal proteolytic system that may play an important role in the processing of biologically active peptides and enzymes, as well as in intracellular metabolism. We report that at least two of its subunits of MW 28,800 (S2) and 27,000 (S3) are phosphorylated by a cAMP-dependent protein kinase (PK-A) that copurifies with the complex isolated from bovine pituitaries. The cAMP-induced phosphorylation was time dependent and inhibited by a PK-A inhibitor. Although not an integral part of the complex, PK-A activity was still present even in 1700-fold-purified and apparently homogeneous preparations by criteria of nondissociating polyacrylamide gel electrophoresis. Furthermore, we present evidence that the copurification of the two enzymes is not species or tissue specific, or dependent on a single method of purification. The copurifying kinase was stimulated 10-fold by cAMP (10 microM) and 2- to 3-fold by a peptide substrate of the MPC, but was unaffected by protein kinase C activators (calcium and a phospholipid mixture). These findings suggest that protein phosphorylation may represent a mechanism for regulating the activity of the multicatalytic proteinase complex.

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          Author and article information

          Journal
          Archives of Biochemistry and Biophysics
          Archives of Biochemistry and Biophysics
          Elsevier BV
          00039861
          November 1990
          November 1990
          : 283
          : 1
          : 68-74
          Article
          10.1016/0003-9861(90)90613-4
          2173492
          48728f35-02a0-4797-893d-1e19cdf2659e
          © 1990

          http://www.elsevier.com/tdm/userlicense/1.0/

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