PURIFICATION AND MOLECULAR-CLONING OF CHYMASE FROM HUMAN TONSILS

A chymotrypsin-like protease was purified to homogeneity from human to nsils by a series of chromatographic procedures. The purified enzyme g ave 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-termina l oligonucleotide primer and a conserved C-terminal primer of the chym ase family. The deduced amino acid sequence of the isolated clone was identical to that of human chymase in connective tissue-type mast cell s from heart except for a Ser instead of a Cys at the N-terminal 7th p osition.