title: Effect of different isomers of dihydroxybenzoic acids (DBA) on the rate of DL-dopa oxidation by mushroom tyrosinase.
abstract: Dihydroxybenzoic acids (DBA), such as 3,4-DBA, 3,5-DBA, and 2,4-DBA--at all concentrations tested--inhibited the rate of DL-DOPA oxidation to dopachrome (lambda max = 475 nm) by mushroom tyro0sinase. 2,3-DBA and 2,5-DBA at relatively low concentration had a synergistic effect on the reaction, whereas at relatively high concentrations they inhibited the rate of DL-DOPA oxidation. The synergistic effect of 0.6-13.3 mM 2,3-DBA on the rate of DL-DOPA oxidation to dopachrome (lambda max = 475 nm) was found to be due to the ability of 2,3-DBA-o-quinone (formed by the oxidation of 2,3-DBA by mushroom tyrosinase or by sodium periodate) to oxidize DL-DOPA to dopachrome (via dopaquinone) non-enzymatically. A similar explanation is likely to be valid for the synergism exerted by 2,5-DBA on the rate of DL-DOPA oxidation by mushroom tyrosinase.
authors.affiliation: Department of Food Science, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel.
authors.forename: F
authors.initials: F
authors.lastname: Schved
authors.forename: V
authors.initials: V
authors.lastname: Kahn
mesh_terms: D001487:Basidiomycota / Q000201:enzymology; D004295:Dihydroxyphenylalanine / Q000378:metabolism*; D004357:Drug Synergism; D005841:Gentisates; D062385:Hydroxybenzoates / Q000494:pharmacology*; D007536:Isomerism; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism*; D008956:Models, Chemical; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D005841:Gentisates; D062385:Hydroxybenzoates; D010940:Plant Proteins; C009091:protocatechuic acid; D007980:Levodopa; D004295:Dihydroxyphenylalanine; C009135:2,3-dihydroxybenzoic acid; D014442:Monophenol Monooxygenase; C010925:2,5-dihydroxybenzoic acid