Purification and molecular cloning of chymase from human tonsils

Abstract
A chymotrypsin‐like protease was purified to homogeneity from human tonsils by a series of Chromatographie procedures. The purified enzyme gave a single protein band with an apparent molecular mass of 30 kDa on SDS‐PAGE. The sequence of the first 21 amino acids at the N‐terminus of the enzyme was determined. A cDNA for the enzyme was cloned by PCR amplification from extracted tonsillar mRNA using a supposed N‐terminal oligonucleotide primer and a conserved C‐terminal primer of the chymase family. The deduced amino acid sequence of the isolated clone was identical to that of human chymase in connective tissue‐type mast cells from heart except for a Ser instead of a Cys at the N‐terminal 7th position.