אסיף מאגר המחקר החקלאי

Effect of benzoic acid and some of its derivatives on the rate of DL-DOPA oxidation by mushroom tyrosinase

Year:

1997

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Volume :

21

Co-Authors:

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

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Abstract:

Vanillic acid and salicylic acid inhibited the rate of dihydroxyphenylalanine (DL-DOPA) oxidation to dopachrome (λmax = 475 nm) by tyrosinase at all concentrations tested. Benzoic acid and p-hydroxybenzoic acid (PHBA), at relatively low concentrations, slightly stimulated the rate of DL-DOPA oxidation, whereas at higher concentrations each inhibited the reaction. p-Hydroxybenzoic acid methyl ester (PHBAME), at relatively low concentrations, had a pronounced synergistic effect on the reaction, whereas at relatively high concentrations it inhibited the rate of DL-DOPA oxidation. The synergistic effect of 1.6-6.6 mM PHBAME on the rate of DL-DOPA oxidation to dopachrome was found to be only an apparent effect due to the ability of PHBAME to be hydroxylated very slowly by tyrosinase to a yellow pigmented product(s) with DL-DOPA serving as a reductant (AH2) for the hydroxylation reaction, thus hastening the conversion of PHBAME to pigmented product(s). Vanillic acid, salicylic acid, benzoic acid and PHBA could not be hydroxylated by tyrosinase.

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