Isolation of kidney brush border gamma-glutamyl transpeptidase from urine by specific antibody gel chromatography.

The IgG fraction of antiserum directed against gamma-glutamyl transpeptidase (gammaGTP, EC 2.3.2.2) isolated from human kidney brush border membranes after limited proteolysis, was covalently bound to cyanogen bromide-activated Sepharose. With this antibody-gel, gammaGTP present in the urine of patients as a result of tubular damage was immunospecifically prepared by affinity chromatography. The enzyme isolated from the urine samples gave a complete cross-reaction wiht gammaGTP artificially cleaved off from brush border fragments. Since labelled anti-gammaGTP sera gave a specific immunofluorescence only of the luminal portion of cortical tubule, the use of immunosorption chromatography appears to be an important approach for the isolation of urinary kidney tissue antigens of a defined origin.