PHOSPHORYLATION OF THE MULTICATALYTIC PROTEINASE COMPLEX FROM BOVINE PITUITARIES BY A COPURIFYING CAMP-DEPENDENT PROTEIN-KINASE
PHOSPHORYLATION OF THE MULTICATALYTIC PROTEINASE COMPLEX FROM BOVINE PITUITARIES BY A COPURIFYING CAMP-DEPENDENT PROTEIN-KINASE
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DOI：
10.1016/0003-9861(90)90613-4
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发表时间：
1990-11-15
影响因子：
3.9
通讯作者：
WILK, S
中科院分区：
文献类型：
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作者：
PEREIRA, ME;WILK, S
多酶解酶复合体(MPC)是一种主要的非溶酶体蛋白分解系统，在生物活性多肽和酶的加工以及细胞内代谢过程中可能发挥重要作用。我们报道了它的至少两个亚基Mw 28,800(S2)和27,000(S3)被cAMP依赖的蛋白激酶(PK-A)磷酸化，PK-A与从牛脑垂体中分离的复合体相互作用。CAMP诱导的磷酸化是时间依赖的，并被PK-A抑制剂抑制。尽管不是复合体的组成部分，但即使在1700倍纯化和表面上均一的制剂中，PK-A活性仍然存在，以非解离聚丙烯酰胺凝胶电泳法为标准。此外，我们提出的证据表明，这两种酶的相互作用不是物种或组织特有的，也不依赖于单一的纯化方法。CAMP(10微米)和MPC的多肽底物分别刺激10倍和2-3倍，但不受蛋白激酶C激活剂(钙和磷脂混合物)的影响。这些发现表明，蛋白磷酸化可能是调节多催化蛋白水解酶复合体活性的一种机制。
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 .mu.M) 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.