Mast cell chymase (EC 3.4.21.39), a member of the granzyme subfamily of the S1 family of peptidases, cleaves chymase C-terminal to Phenylalanine, Tyrosine, Tryptophan, and Leucine residues (in order of preference). Chymase is stored in mast cell granules within the cell and is the major secreated mast cell protease. Secreated mast cell chymase is believed to be involved in extracellular matrix degradation, vasoactive peptide generation, and regulation of gland secreation.