title: Inhibitory effect of 4-cyanobenzaldehyde and 4-cyanobenzoic acid on mushroom (Agaricus bisporus) tyrosinase.
abstract: Mushroom tyrosinase (EC 1.14.18.1), a copper containing oxidase, catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones. In the current study, the effects of 4-cyanobenzaldehyde and 4-cyanobenzoic acid on the monophenolase and diphenolase activities of mushroom tyrosinase have been studied. The results show that 4-cyanobenzaldehyde and 4-cyanobenzoic acid can inhibit both the monophenolase activity and the diphenolase activity of mushroom tyrosinase. The lag phase of tyrosine oxidation catalyzed by the enzyme was obviously lengthened, and the steady-state activity of the enzyme decreased sharply. 1.0 mM 4-cyanobenzaldehyde and 4-cyanobenzoic acid can lengthen the lag phase from 78 s to 134 and 115 s, respectively. Both 4-cyanobenzaldehyde and 4-cyanobenzoic acid can lead to reversible inhibition of the enzyme. The IC50 values of 4-cyanobenzaldehyde and 4-cyanobenzoic acid were estimated as 0.62 and 2.45 mM for monophenolase and as 0.72 and 1.40 mM for diphenolase, respectively. A kinetic analysis shows that 4-cyanobenzaldehyde and 4-cyanobenzoic acid are mixed-type inhibitors for the diphenolase. The apparent inhibition constants for 4-cyanobenzaldehyde and 4-cyanobenzoic acid binding with both the free enzyme and the enzyme-substrate complex have been determined and compared.
authors.affiliation: The key laboratory of Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, People's Republic of China.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Chen
authors.forename: Qing-Xi
authors.initials: QX
authors.lastname: Chen
authors.forename: Ling
authors.initials: L
authors.lastname: Qiu
authors.forename: Kang-Kang
authors.initials: KK
authors.lastname: Song
authors.forename: Huang
authors.initials: H
authors.lastname: Huang
mesh_terms: D000363:Agaricales / Q000187:drug effects / Q000201:enzymology*; D000364:Agaricus / Q000201:enzymology*; D001547:Benzaldehydes / Q000494:pharmacology*; D001565:Benzoates / Q000494:pharmacology*; D002384:Catalysis; D004156:Catechol Oxidase / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019649:Food Industry; D020128:Inhibitory Concentration 50; D007700:Kinetics; D007980:Levodopa / Q000737:chemistry / Q000378:metabolism; D008543:Melanins / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors
chemical_list: D001547:Benzaldehydes; D001565:Benzoates; D004791:Enzyme Inhibitors; D008543:Melanins; D007980:Levodopa; C097383:4-cyanobenzoic acid; C488327:4-cyanobenzaldehyde; D010088:Oxidoreductases; D004156:Catechol Oxidase; C412191:monophenolase; D014442:Monophenol Monooxygenase