title: Covalent modification of mushroom tyrosinase with different amphiphic polymers for pharmaceutical and biocatalysis applications.
abstract: Two different poly(ethylene glycol) derivatives (linear, mol wt 5000 and a branched form, mol wt 10000) and a new polymer (poly-[acryloylmorfoline], mol wt 5500) were covalently bound to the enzyme tyrosinase. The polymer-protein conjugates were studied with a view to their potential pharmaceutical application and to their use for the bioconversion of phenolic substrates in organic solvents. Vmax and Km for the dopa-dopaquinone conversion, thermostability, stability toward inactivation by dopa oxidation products, half-life in blood circulation, and behavior in organic solvents for the different adducts were investigated. Arrhenius plots for the dopa-dopaquinone conversion were also obtained in order to study the effects of temperature on the different enzyme forms. Covalent attachment of the polymers increased enzyme stability in aqueous solution and the solubility in organic solvents. However, organic solvent solubilization brought about loss of enzyme conformation as assessed by CD measurements, which is accompanied by a nonreversible loss of catalytic activity.
authors.affiliation: Department of Pharmaceutical Sciences, Biologicamente Attivi del CNR, University of Padova, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Morpurgo
authors.forename: O
authors.initials: O
authors.lastname: Schiavon
authors.forename: P
authors.initials: P
authors.lastname: Caliceti
authors.forename: F M
authors.initials: FM
authors.lastname: Veronese
mesh_terms: D000818:Animals; D001487:Basidiomycota / Q000201:enzymology*; D016227:Benzoquinones / Q000378:metabolism; D002384:Catalysis; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives / Q000378:metabolism; D004795:Enzyme Stability; D006207:Half-Life; D006358:Hot Temperature; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics; D010636:Phenols / Q000378:metabolism; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D013678:Technology, Pharmaceutical; D013816:Thermodynamics
chemical_list: D016227:Benzoquinones; D010636:Phenols; D011108:Polymers; D011092:Polyethylene Glycols; D004295:Dihydroxyphenylalanine; C035157:dopaquinone; D014442:Monophenol Monooxygenase