title: Active site residue involvement in monoamine or diamine oxidation catalysed by pea seedling amine oxidase.
abstract: The structures of copper amine oxidases from various sources show good similarity, suggesting similar catalytic mechanisms for all members of this enzyme family. However, the optimal substrates for each member differ, depending on the source of the enzyme and its location. The structural factors underlying substrate selectivity still remain to be discovered. With this in view, we examined the kinetic behaviour of pea seedling amine oxidase with cadaverine and hexylamine, the first bearing two, and the second only one, positively charged amino group. The dependence of K(m) and catalytic constant (k(c)) values on pH, ionic strength and temperature indicates that binding of the monoamine is driven by hydrophobic interactions. Instead, binding of the diamine is strongly facilitated by electrostatic factors, controlled by polar side-chains and two titratable residues present in the active site. The position of the docked substrate is also essential for the participation of titratable amino acid residues in the following catalytic steps. A new mechanistic model explaining the substrate-dependent kinetics of the reaction is discussed.
authors.affiliation: Dipartimento di Chimica Biologica and INBB, Università di Padova, Padova, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Di Paolo
authors.forename: Michele
authors.initials: M
authors.lastname: Lunelli
authors.forename: Monika
authors.initials: M
authors.lastname: Fuxreiter
authors.forename: Adelio
authors.initials: A
authors.lastname: Rigo
authors.forename: Istvan
authors.initials: I
authors.lastname: Simon
authors.forename: Marina
authors.initials: M
authors.lastname: Scarpa
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry / Q000378:metabolism*; D000588:Amines / Q000378:metabolism; D002103:Cadaverine / Q000378:metabolism; D002384:Catalysis; D020134:Catalytic Domain; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D008995:Monoamine Oxidase / Q000378:metabolism; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D018532:Pisum sativum / Q000201:enzymology; D036226:Seedlings / Q000201:enzymology; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D000588:Amines; C007940:hexylamine; D006631:Amine Oxidase (Copper-Containing); D008995:Monoamine Oxidase; D002103:Cadaverine