title: pH-dependent inhibition of mushroom tyrosinase by N-substituted N-nitrosohydroxylamines.
abstract: Several synthetic N-substituted N-nitrosohydroxylamines were found to inhibit mushroom tyrosinase in a pH-dependent manner regardless of the N-substituent. The inhibitory activity, or pI(50) ( - log [IC(50), M]) value, linearly decreased as the pH of the media increased. The inhibitory activities of tested N-substituted N-nitrosohydroxylamines at pH 6.8 and 5.8 were found to be almost 10 times and 100 times greater than at pH 7.8, respectively. The types of inhibition were different at pH 6.8 and 5.8. These results suggest that the inhibitory effect of N-substituted N-nitrosohydroxylamines is caused by the non-ionized form of the inhibitor. Furthermore, the mechanism of inhibition depends on the interaction between the inhibitor and the active site of tyrosinase at different pH values.
authors.affiliation: School of Medicine, Keio University, Yokohama, Japan. shiino@signalcreation.com
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Shiino
authors.forename: Yumi
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Kazuo
authors.initials: K
authors.lastname: Umezawa
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D019817:Benzoic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D006877:Hydroxamic Acids / Q000494:pharmacology; D006898:Hydroxylamines / Q000494:pharmacology*; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D009603:Nitroso Compounds / Q000494:pharmacology*; D011753:Pyrones / Q000494:pharmacology; D014334:Tropolone / Q000494:pharmacology
chemical_list: D006877:Hydroxamic Acids; D006898:Hydroxylamines; D009603:Nitroso Compounds; D011753:Pyrones; C011890:kojic acid; D014334:Tropolone; D019817:Benzoic Acid; D014442:Monophenol Monooxygenase; C006696:benzohydroxamic acid