Kahn, V., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50 250, Israel
Ben-Shalom, N., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50 250, Israel
Zakin, V., Department of Food Science, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50 250, Israel

Kojic acid inhibited mushroom tyrosinase, as judged by the inhibition it exerted on the rate of oxygen uptaked during N-acetyldopamine (NADA) oxidation. Preincubation of mushroom tyrosinase with kojic acid did not result in the inactivation of the enzyme (irreversible loss of activity). Kojic acid had a pronounced effect on the spectrum of product(s) obtained when NADA was oxidized by mushroom tyrosinase. In its absence, NADA quinone (λmax = 390 ± 10 nm) was formed; in its presence, a stable final yellow product(s), characterized by a peak at 340 ± 20 nm, was obtained. A maximum level of the final yellow product(s) was formed when the ratio between NADA quinone and kojic acid was 1:1. Spectral data suggest that NADA quinone oxidizes kojic acid to the yellow product(s).