title: Inactivation kinetics of mushroom tyrosinase by cetylpyridinium chloride.
abstract: Cetylpyridinium chloride (CPC) was found to inactivate tyrosinase from mushroom (Agaricus bisporus). CPC can bind to the enzyme molecule and induce the enzyme conformation changes. The fluorescence intensity (at 338.4 nm) of the enzyme decreased distinctly with increasing CPC concentrations, and a new little fluorescence emission peak appeared near 372 nm. The inactivation of the enzyme by CPC had first been studied by using the kinetic method of the substrate reaction described by Tsou. The results showed that the enzyme was inactivated by a complex mechanism that had not been previously identified. The enzyme first quickly binds with CPC reversibly and then undergoes a slow irreversible inactivation. The inactivation reaction is a single molecule reaction and the apparent inactivation rate constant is a saturated trend being independent of CPC concentration if the concentration is sufficiently high. The micro rate constants of inactivation and the association constant were determined.
authors.affiliation: Key laboratory of Ministry of Education for Cell Biology and Tumor Cell Engineering, Department of Biology, Xiamen University, Xiamen 361005, People's Republic of China. chenqx@jingxian.xmu.edu.cn
authors.forename: Qing-Xi
authors.initials: QX
authors.lastname: Chen
authors.forename: Huang
authors.initials: H
authors.lastname: Huang
authors.forename: Isao
authors.initials: I
authors.lastname: Kubo
mesh_terms: D000364:Agaricus / Q000201:enzymology*; D002594:Cetylpyridinium / Q000494:pharmacology*; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D007980:Levodopa; D002594:Cetylpyridinium; D014442:Monophenol Monooxygenase