Kahn, V., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Zakin, V., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel

2,4,5-trihydroxybutyrophenone (2,4,5-THBP), in the presence of hydrogen peroxide (H2O2), is a substrate for horseradish peroxidase (HRP) with a Km value of 2.5 mM. An intermediate red product(s), probably 2,4,5-THBP quinone, characterized by a peak at 490-500 nm, was detected and the time course of its conversion to the final red product(s) was studied. The relationships between the rate of 2,4,5-THBP oxidation to pigmented product(s) as a function of various concentrations of H2O2, 2,4,5-THBP and HPR are described.