Structural features of two kininase I-type enzymes revealed by molecular cloning

Kininase I-type carboxypeptidases remove a single C-terminal Arg residue from kinins. The circulating kininase I (carboxypeptidase N) contains two types of subunits: a 50 kDa catalytic subunit and an 83 kDa carrier subunit which protects the active subunit in blood. The 83 kDa subunit contains 12 leucine-rich tandem repeats, similar in sequence to other proteins with binding functions. Human carboxypeptidase M is a widely distributed "tissue kininase I" bound to plasma membranes. It has 41% sequence identity with the 50 kDa subunit of carboxypeptidase N and may regulate the activity of kinins and other peptides at the cell surface.