Some Old and Some New Ideas on Kinin Metabolism

Enzymes that hydrolyze kinins are known under the collective term of "kininases." This short review surveys kininase I- and II-type enzymes. For the sake of simplicity, we call carboxypeptidases that remove the C-terminal arginine of kinins kininase I-type enzymes. Plasma carboxypeptidase N and the cell membrane-bound carboxypeptidase M belong here. Kininase II enzymes release the C-terminal dipeptide Phe-Arg; angiotensin I-converting enzyme and neutral endopeptidase 24.11 (enkephalinase) are prominent members of this subgroup of proteins. The primary sequence of five proteins of the four human kininases (including the catalytic and regulatory subunits of carboxypeptidase N) were deduced from the nucleotide sequence of their cDNAs. The structure and properties of these enzymes are briefly discussed.