Confirmation of direct angiotensin formation by kallikrein

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Abstract
The previous preliminary observation that hog pancreas kallikrein (EC 3.4.21.35) directly liberated an angiotensin-like substance from human plasma Cohn fraction IV-4 at an acidic pH of 4.0-5.0 was confirmed. First, the possibility of proangiotensin or des-Asp1-angiotensin being the pressor substance was ruled out by TLC. Second, the pressor substance was purified by Sephadex G-25 and Bio-Gel P-2 gel filtration and finally by high-performance liquid chromatography. The amino acid composition of the isolated pressor substance (residues/mol) was: Asp, 1.03; Val, 1.03; Ile, 1.00; Tyr, 0.69; Phe, 1.04; His, 0.91; Arg, 0.86; Pro, 0.86. This composition was identical with that of angiotensin. Since the reaction mixture was not contaminated with common proteolytic enzymes, such as trypsin, chymotrypsin, renin, cathepsin D and proangiotensin-converting enzyme, and other enzymes activated by kallikrein, it is clear that hog kallikrein directly produces angiotensin in vitro.