Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.64 (proteinase K)
 4,071 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated connexin-32s from rat and mouse liver are proteolyzed in vitro by the intracellular Ca(2+)-dependent neutral proteases, mu-calpain and m-calpain, producing a major fragment of 26 kDa. Connexin-26 is not proteolyzed by calpain. Calpain cleaves connexin-32 at its C-terminal end as shown by 125I-calmodulin binding experiments. Connexin-32, but not connexin-26, is phosphorylated by both protein kinase A and protein kinase C in serine residues and the sites of phosphorylation by both kinases remain in the major 26-kDa fragment resulting from calpain proteolysis. Phosphorylation of connexin-32 by protein kinase C, but not by protein kinase A, prevents the proteolytic attack of mu-calpain and m-calpain. Phosphorylation of connexin-32 by protein kinase A and protein kinase C does not prevent its proteolysis by papain, alpha-chymotrypsin, proteinase K, and trypsin.
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PMID:Phosphorylation of connexin-32 by protein kinase C prevents its proteolysis by mu-calpain and m-calpain. 839 Sep 88

Calpain and calpastatin have been demonstrated to play many physiological roles in a variety of systems. It, therefore, appears important to study their localization and association in different suborganelles. Using immunoblot studies, we have identified 80 kDa m-calpain in both lumen and membrane of ER isolated from bovine pulmonary artery smooth muscle. Treatment of the ER with Na(2)CO(3) and proteinase K demonstrated that 80 kDa catalytic subunit and 28 kDa regulatory subunit (Rs) of m-calpain, and the 110-kDa and 70-kDa calpastatin (Cs) forms are localized in the cytosolic side of the ER membrane. Coimmunoprecipitation studies revealed that m-calpain is associated with calpastatin in the cytosolic face of the ER membrane. We have also identified m-calpain activity both in the ER membrane and lumen by casein-zymography. The casein-zymogram has also been utilized to demonstrate differential pattern of the effects of reversible and irreversible cysteine protease inhibitors on m-calpain activity. Thus, a potential site of Cs regulation of m-calpain activity is created by positioning Cs, 80 kDa and 28 kDa m-calpain in the cytosolic face of ER membrane. However, such is not the case for the 80-kDa m-calpain found within the lumen of the ER because of the conspicuous absence of 28 kDa Rs of m-calpain and Cs in this locale.
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PMID:Localization of m-calpain and calpastatin and studies of their association in pulmonary smooth muscle endoplasmic reticulum. 1765 25