אסיף מאגר המחקר החקלאי

p-Hydroxyphenylpropionic acid (PHPPA) and 3,4-dihydroxyphenylpropionic acid (3,4-DPPA) as substrates for mushroom tyrosinase

Year:

1999

Source of publication :

Authors :

Volume :

23

Co-Authors:

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

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Abstract:

p-Hydroxyphenylpropionic acid (PHPPA) and 3,4-dihydroxyphenylpropionic acid (3,4-DPPA) serve as substrates for tyrosinase. The Km value of 3,4-DPPA for tyrosinase is 1.3 mM. The yellow o-quinone of 3,4-DPPA (4-carboxyethyl-o-benzoquinone) (λmax = 400nm), is detected initially and it is then converted to a red product(s) (λmax = 480±10 nm), the o-quinone of 6,7-dihydroxy 3-dihydrocumarin (dihydroesculetin). When the concentration of the latter is relatively high, it polymerizes to a final brown product(s), characterized by an ill-defined spectrum. H2O2 shortens the lag period of PHPPA hydroxylation, hastens the conversion of the yellow o-quinone of 3,4-DPPA to the red o-quinone of dihydroesculetin, and prevents the polymerization of the latter to the final brown product(s). The relatively unstable o-quinone of 3,4-DPPA interacts with amines such as hydroxylamine (NH2OH), p-aminosalicylic acid (PASA) and p-aminobenzoic acid (PABA), forming relatively stable final product(s) characterized by different spectra from those formed in their absence. Acetohydroxamic acid (AHA) and salicylhydroxamic acid (SHAM) each has an effect on the spectrum of product(s) obtained when 3,4-DPPA is oxidized by tyrosinase, indicating that these hydroxamic acids derivatives interact with the o-quinone of 3,4-DPPA. The spectrum of the final product(s) was also different when 3,4-DPPA was oxidized by tyrosinase in the presence of benzenesulfinic acid than in its absence, suggesting the formation of a stable phenylsulfonyl derivative.

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