2002 Volume 51 Issue 12 Pages 1183-1185
The magnitude of the steady-state current by a sulfhydryl compound at a dialysis membrane (molecular cut off: 5000) coverd cobalt phthalocyanine-embedded electrode was inversly proportional to the molecular weight. That is, the currents by 1 μM glutathione (GSH), glutamylcysteine and cysteine at 200 mM and at pH 8.3 were 0.07, 0.14 and 0.39 nA, respectively. The activity of γ-glutamyltransferase (γ-GT) in serum was determined by measuring the current increase for a given time due to the degradation of GSH to cysteinylglysine in a 0.1 M tris buffer of pH 8.3 containing 1.2 mM GSH, 50 mM glysylglysine and 5 mM EDTA. The activities of γ-GT determined amperometrically using GSH as a substrate for sixteen serum samples were in good agreement with those determined by a colorimetric method using γ-glutamy1-3-carboxy-4-nitroanilide (Glucana) a as substrate (r=0.98).
