A human neutrophil-dependent pathway for generation of angiotensin II. Purification of the product and identification as angiotensin II.

Abstract

A human neutrophil lysosomal protease interacts at physiologic pH with a 62,000--67,000-mol wt plasma protein substrate to generate a vasoactive, smooth muscle-contracting "neutral" peptide. The peptide product of this system, previously designated the "neutral" peptide-generating pathway, was generated from purified components and purified by Bio-Gel P2 gel filtration and reverse-phase high performance liquid chromatography with a 50--60% yield of starting activity. The purified peptide had an amino acid composition of Asx, Pro, Val, Ile, Tyr, Phe, His, Arg, a composition identical to that of angiotensin II. The peptide and synthetic angiotensin II each filtered at 48--52% bed volume on Bio-Gel P2, had an isoelectric point of Ph 7.8--8.1 at 4 degrees C, migrated 3 cm toward the cathode during pH 6.4 low-voltage paper electrophoresis, and had a retention time of 44.8 min during reverse-phase high-performance liquid chromatography. In addition, the functional activity of the peptide at each purification step correlated with angiotensin II content determined by specific radioimmunoassay. The amino acid sequence of 25 nmol of the peptide was Asp-Arg-Val-Try-Ile-His-Pro-Phe, the same covalent structure as that of angiotensin II. Therefore, under physiologic conditions, in the absence of renin or angiotensin converting enzyme, a human neutrophil neutral protease cleaves a plasma protein to yield angiotensin II. This pathway provides a mechanism through which the neutrophil may alter local blood flow during inflammation by generation of a potent vasoactive peptide.