A new assay method of gamma-glutamyltransferase with 4-aminobenzoate hydroxylase from Agaricus bisporus as a coupling enzyme

We have developed a new ultraviolet spectrophotometric method for measureme nt of serum gamma-glutamyltransferase activity. The principle of the method is as follows. Using L-gamma-glutamyl-3-chloro-4-aminobenzoate as the dono r substrate, 3-chloro-4-aminobenzoate formed upon transfer of the gamma-glu tamyl moiety from the donor substrate to the acceptor substrate glycylglyci ne is stoichiometrically converted to 3-chloro-4-hydroxyaniline by 4-aminob enzoate hydroxylase from Agaricus bisporus, coupled with the oxidation of N ADH to NAD(+), and the resulting decrease in absorbance at 340 nm is monito red. The results obtained indicate that there is a good possibility to esta blish an ultraviolet spectrophotometric method for measurement of serum gam ma-glutamyltransferase activity using L-gamma-glutamyl-3-chloro-4-aminobenz oate as the donor substrate and 4-aminobenzoate hydroxylase from Agaricus b isporus as a coupling enzyme. (C) 1999 Elsevier Science BN. All rights rese rved.