title: Regulation of rat mast cell protease 1 activity. Protease inhibition is prevented by heparin proteoglycan.
abstract: Rat mast cell protease 1 (RMCP-1) is a chymotrypsin-like serine protease (chymase) that is specifically expressed by connective-tissue-type mast cells. It is stored in the secretory granules of the cells in a complex with heparin proteoglycan, and the chymase/heparin proteoglycan complexes are released following mast cell activation. The present study was undertaken to examine if the association with heparin proteoglycan influenced the regulation of RMCP-1 by various macromolecular protease inhibitors. Endogenous mast cell heparin proteoglycan was shown to significantly block the inhibition of RMCP-1 by the serpins alpha 1-protease inhibitor and alpha 1-antichymotrypsin, as well as the inhibition by alpha 2-macroglobulin, soybean trypsin inhibitor and plasma. The blocking of protease inhibition showed an optimum at a RMCP-1/proteoglycan ratio of 5:1 (by mass), corresponding to approximately 80 RMCP-1 molecules bound/proteoglycan molecule. Chymase activity present on intact peritoneal mast cells, i.e. present in its native complex with heparin proteoglycan, was also shown to be largely resistant to inhibition by alpha 1-antichymotrypsin and alpha 1-protease inhibitor. Heparin 10-saccharides and 20-saccharides were inefficient in preventing the interaction of RMCP-1 with alpha 1-antichymotrypsin, whereas pig mucosal heparin (approximately 50 monosaccharide units) blocked protease inhibition. We have previously shown that heparin potentiates the catalytic activity of RMCP-1 and, in the present study, we show that the mechanism for chymase activation involves a sixfold reduction of the Km,app value of RMCP-1 for the chromogenic substrate S-2586. Thus, the association of mast cell chymase with heparin proteoglycan may serve both to potentiate the catalytic activity of the enzyme and to increase the life-span of the chymases by preventing their inhibition after exocytosis.
authors.affiliation: Swedish University of Agricultural Sciences, Dept. of Veterinary Medical Chemistry, Uppsala, Sweden.
authors.forename: G
authors.initials: G
authors.lastname: Pejler
authors.forename: L
authors.initials: L
authors.lastname: Berg
mesh_terms: D000818:Animals; D053818:Chymases; D005260:Female; D006493:Heparin / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D011480:Protease Inhibitors / Q000378:metabolism / Q000494:pharmacology; D011509:Proteoglycans / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D015843:Serpins / Q000378:metabolism / Q000494:pharmacology; D013552:Swine
chemical_list: D008024:Ligands; D011480:Protease Inhibitors; D011509:Proteoglycans; D015843:Serpins; C036090:heparin proteoglycan; D006493:Heparin; D012697:Serine Endopeptidases; D053818:Chymases; C509231:Mcpt1 protein, rat