title: Electrostatic compared with hydrophobic interactions between bovine serum amine oxidase and its substrates.
abstract: A steady-state kinetic study of bovine serum amine oxidase activity was performed, over a wide range of pH values (5.4-10.2) and ionic strength (10-200 mM), using various (physiological and analogue) substrates as specific probes of the active-site binding region. Relatively small changes in k (cat) values (approx. one order of magnitude) accompanied by marked changes in K(m) and k(cat)/K(m) values (approx. six orders of magnitude) were observed. This behaviour was correlated with the presence of positively charged groups or apolar chains in the substrates. In particular, it was found that the docking of the physiological polyamines, i.e. spermidine and spermine, appears to be modulated by three amino acid residues of the active site, which we have named L(-)H(+), G(-)H(+) and IH(+), characterized by p K (a) values of 6.2+/-0.2 [Di Paolo, Scarpa, Corazza, Stevanato and Rigo (2002) Biophys. J. 83, 2231-2239], 8.2+/-0.3 and 7.8+/-0.4 respectively. The electrostatic interaction between the protonated substrates and the enzyme containing the residues L(-)H(+), G(-)H(+) and IH(+) in the deprotonated form, the on/off role of the IH(+) residue and the role of hydrophobic interactions with substrates characterized by apolar chains are discussed.
authors.affiliation: Dipartimento di Chimica Biologica, Università di Padova, Italy.
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Di Paolo
authors.forename: Roberto
authors.initials: R
authors.lastname: Stevanato
authors.forename: Alessandra
authors.initials: A
authors.lastname: Corazza
authors.forename: Fabio
authors.initials: F
authors.lastname: Vianello
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Lunelli
authors.forename: Marina
authors.initials: M
authors.lastname: Scarpa
authors.forename: Adelio
authors.initials: A
authors.lastname: Rigo
mesh_terms: D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008962:Models, Theoretical; D055672:Static Electricity; D013379:Substrate Specificity
chemical_list: D006631:Amine Oxidase (Copper-Containing)