Regulation of rat mast cell protease 1 activity. Protease inhibition is prevented by heparin proteoglycan

Eur J Biochem. 1995 Oct 1;233(1):192-9. doi: 10.1111/j.1432-1033.1995.192_1.x.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chymases
  • Female
  • Heparin / analogs & derivatives*
  • Heparin / metabolism
  • Heparin / pharmacology
  • In Vitro Techniques
  • Kinetics
  • Ligands
  • Mast Cells / drug effects
  • Mast Cells / enzymology*
  • Mast Cells / metabolism
  • Protease Inhibitors / metabolism
  • Protease Inhibitors / pharmacology
  • Proteoglycans / metabolism
  • Proteoglycans / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Serine Endopeptidases / chemistry
  • Serine Endopeptidases / metabolism*
  • Serpins / metabolism
  • Serpins / pharmacology
  • Swine

Substances

  • Ligands
  • Protease Inhibitors
  • Proteoglycans
  • Serpins
  • heparin proteoglycan
  • Heparin
  • Serine Endopeptidases
  • Chymases
  • Mcpt1 protein, rat