title: Effect of AOT on enzymatic activity of the organic solvent resistant tyrosinase from Streptomyces sp. REN-21 in aqueous solutions and water-in-oil microemulsions.
abstract: The effect of AOT (sodium-bis(2-ethylhexyl sulfosuccinate)) on enzymatic activity of the organic solvent resistant tyrosinase (OSRT) in aqueous phosphate buffer solutions and in water-in-oil microemulsions of the water/AOT/isooctane system has been investigated. In contrast to mushroom tyrosinase, AOT does not activate OSRT in aqueous solutions, altering its activity very little at concentrations lower than 2 mM. Increasing contents of AOT in isooctane reduce the observed initial reaction rates of oxidation of t-butylcatechol (tBC) and 4-methylcatechol (4-MC). Similarly to mushroom tyrosinase, the effect has been described using an equation based on preferential binding of the substrates by surfactant interface layers. The apparent Michaelis-Menten substrate binding constants increase linearly with AOT concentration (with slopes of 0.12+/-0.02 and 0.051+/-0.006 for tBC and 4-MC, respectively), and the effective enzyme turnover number in the microemulsions remains practically constant.
authors.affiliation: Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, 30 239 Kraków, Poland. ncrodaki@cyf-kr.edu.pl
authors.forename: Janina
authors.initials: J
authors.lastname: Rodakiewicz-Nowak
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ito
mesh_terms: D004143:Dioctyl Sulfosuccinic Acid / Q000737:chemistry* / Q000494:pharmacology; D004655:Emulsions / Q000737:chemistry*; D004789:Enzyme Activation / Q000187:drug effects; D008832:Microchemistry; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism; D009795:Octanes / Q000737:chemistry; D009821:Oils / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry*; D013302:Streptomyces / Q000201:enzymology*; D013386:Succinates / Q000737:chemistry* / Q000494:pharmacology; D014867:Water / Q000737:chemistry*
chemical_list: D004655:Emulsions; D009795:Octanes; D009821:Oils; D012996:Solutions; D013386:Succinates; D014867:Water; D004143:Dioctyl Sulfosuccinic Acid; D014442:Monophenol Monooxygenase; C045798:2,2,4-trimethylpentane