A kinetic assay for human urinary kallikrein determination

A simple kinetic method for human urinary kallikrein determination is proposed. In this assay, the release of p-nitroaniline from the chromogenic substrate S-2266 at 37 degrees C and pH 8.2 is followed spectrophotometrically at 405 nm. The delta A/5 min (0-5 min) interval was chosen. This assay was shown to have good sensitivity since enzyme concentrations as low as 0.00125 KU/ml could be measured. The use of dialyzed urines minimizes the interferences associated with high urinary salt concentration. Because of its precision and reproducibility, this kinetic assay may be proposed in clinical investigation.