The amount of angiotensinase activity in plasma and its impact on PRA measurement has been shown in prior studies.
A range of angiotensinase activities has been described, and recently ACE 2, a new angiotensin-converting enzyme, was described that generates Ang I 1-9 by the removal of a single C-terminal amino acid (18).
Kodish ME, Katz FH Plasma renin concentration: comparison of angiotensinase inhibitors and correlation with plasma renin activity and aldosterone.
AlaAP, which exhibits broad substrate specificity, may hydrolyze bradykinins (4) and enkephalins (16), and may also act as an angiotensinase (17).
Several AP activities (AlaAP, ArgAP, and AspAP), which were significantly modified in the material we analyzed, possess angiotensinase activity.
A method based on a wheat germ agglutinin extraction column combined with high-performance anion-exchange chromatography has been reported as a means to purify and analyze angiotensinase A and aminopeptidase M in human urine and kidney samples (101).
Isolation and partial characterization of angiotensinase A and aminopeptidase M from urine and human kidney by lectin affinity chromatography and high-performance liquid chromatography.
PRA was measured by RIA of angiotensin I in the presence of reagents that inhibit angiotensin I-converting enzyme and angiotensinases
The direct measurement of Ang2 is difficult because of its very low circulating concentrations (3, 4) and extremely short in vivo half-life as it is rapidly degraded to inactive polypeptide fragments by angiotensinases in plasma and tissue (2).
If these conditions are controlled, angiotensinases can be successfully inhibited for up to 18 h, and these extended incubation times negate the necessity of blank subtraction, a major source of variability in some PRA assays (1).