Colorimetric method for assay of serum gamma-glutamyltransferase activity with some L-gamma-glutamyl-carboxyanilides.

A simple method for the assay of serum gamma-glutamyltransferase activity with soluble L-gamma-glutamyl-carboxyanilides is presented. It is based on transformation of aminobenzoic acid liberated by the enzyme into colour complex with 4-dimethyl-aminobenzaldehyde or with 4-dimethylaminocinnamaldehyde in acid medium. Among three carboxyanilides studied the highest enzyme activity was noted with L-gamma-glutamyl-3-carboxyanilide and no activity with L-gamma-glutamyl-2-carboxyanilide. A good correlation was demonstrated for serum gamma-glutamyltransferase activity determined by the new colorimetric method and by the standard one with L-gamma-glutamyl-3-carboxy-4-nitroanilide.