Spectrophotometric assay for urinary N-acetyl-beta-D-glucosaminidase activity

An improved assay for N-acetyl-beta-D-glucosaminidase activity in urine is described that involves (a) gel filtration to separate the enzyme from inhibitors in urine, (b) enzymic hydrolysis of p-nitrophenyl-N-acetyl-beta-D-glucosaminide at pH 4.4, and (c) spectrophotometry of the liberated p-nitrophenylate. Measurements of activity of the enzyme in 58 urine specimens correlated closely (r = 0.9998) with results by an established procedure. The within-run coefficient of variation (CV) was 3.7%; the between-run CV averaged 6.8%. Reference values for the activity were established by assays of urine specimens from 135 healthy persons, age two weeks to 52 years. Efficacy of the assay for detection of nephrotoxicity was demonstrated in rats after experimental induction of reversible renal insufficiency by intraperitoneal injection of nickel chloride. Clinical application of the assay in approximately 1000 patients corroborated its utility for detection and monitoring of renal disorders.