Gamma-glutamyl transpeptidase activity in human urine

The gamma-glutamyl transpeptidase (EC 2.3.2.2) activity of the urine was determined in 369 cases, with L-gamma-glutamyl-p-nitranilide as substrate. Thermally stable, low molecular mass inhibitors were removed by dialysis. The enzyme activity was found to have a mean of 10.57 U/l for the normal neonate population, and a mean of 16.92 U/l for children. A significant increase in activity was observed in pyelonephritis, Alport's syndrome, Wilms' tumour and glomerulopathies. The highest activities were found in kidney diseases associated with renal insufficiency. This non-invasive test can be used for the evaluation of tubular disorders in childhood.