Carboxypeptidase activity in human urine from healthy subjects and renal disease patients

We have attempted to estimate the carboxypeptidase activity in unconcentrated human urine by means of a colorimetric method in which Bz-Gly-Lys is employed as a substrate. Upon addition of both 1.6 mmol/l CoCl2 and 0.18 g/l bovine serum albumin to the assay solution at pH 5.6, the carboxypeptidase activity in human urine can be evaluated. Using our method, the daily excretion of carboxypeptidase in both healthy subjects and patients with renal diseases has been examined. The level is increased in patients with nephrotic glomerulonephritis (24.9 +/- 14.9 (SD) U/day; n = 8) and patients with nephritic glomerulonephritis (11.4 +/- 7.55 (SD) U/day; n = 14) as compared to that in healthy subjects (5.10 +/- 1.88 (SD) U/day; n = 18). However, it is decreased in patients with chronic renal failure (2.70 +/- 2.13 (SD) U/day; n = 12).