Kinetic rate assay of urinary N-acetyl-beta-D-glucosaminidase with 2-chloro-4-nitrophenyl-N-acetyl-beta-D-glucosaminide as substrate.

In this new procedure for determining the activity of N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30; NAG) in urine, a new synthetic substrate, 2-chloro-4-nitrophenyl-N-acetyl-beta-D-glucosaminide is used. No sample blank is required because the activity is determined kinetically. Very high precision is possible, with CVs of less than 3.8% both within-run and between-run. Glucose, ascorbic acid, bilirubin, bromosulfonphthalein, and phenosulfonphthalein do not interfere. The reference interval (mean +/- 2 SD) for healthy subjects was 1.9-11.1 U per gram of creatinine. NAG activity can be determined over a wide range (2-500 U/L) with high sensitivity. The method is suitable for use with various automated analyzers, and it should be useful for screening for renal diseases.