Characterisation of tryptase and a granzyme H-like chymase isolated from equine mastocytoma tissue

Mast cell proteinases are important inflammatory mediators in man and other species, but until now there has been no investigation of the nature of eq uine mast cell proteinases. These studies describe the purification and cha racterisation of two proteolytic components from equine mastocytoma tissue, detected using chromogenic substrates for trypsin and chymotrypsin. Follow ing chromatographic purification, the trypsin-like component was found to b e equine mast cell tryptase by N-terminal amino acid sequencing, showing a close similarity with human tryptase-beta (85% identity over 20 residues). It also had similar subunit molecular size (34-36 kDa by SDS-PAGE) and subs tantially similar cleavage specificity to human tryptase-beta with the subs trates tested. A 32 kDa chymotrypsin-like component was also purified from mastocytoma extract, and termed equine mast cell proteinase-1 (eqMCP-1). Th e N-terminal amino acid sequence of eqMCP-1 was very similar to human granz yme H (95% over 19 residues). Rabbit antisera directed against tryptase and eqMCP-1 both detected equine mast cells by immunohistochemistry, and will be of use in future clinical studies of the relevance of mast cell proteina ses in equine allergic disease. (C) 2001 Elsevier Science B.V. All rights r eserved.