Application of fluorescence polarization to the determination of urinary lysozyme activity.

A fluorescence polarization (FP) technique was applied to the assay of lysozyme activity in human urine. In this assay system, reaction between enzyme and fluorescein-labelled substrate produced a decrease in the fluorescein polarization (P) value. Enzyme activity and rate of decrease of P value exhibited a hyperbolic proportionality between 0.01 mg/L and 10.0 mg/L of lysozyme concentration. The method was compared with a turbidimetric method and the results were comparable with each other. Urinary lysozyme activity in patients with various renal diseases whose renal function had deteriorated was 1.04 +/- 2.55 mg/L (mean +/- S.D.), whereas that of normal controls was 0.13 +/- 0.14 mg/L.