Aromatic aldehydes at the active site of Aldehyde Oxidoreductase from Desulfovibrio gigas: Reactivity and Molecular Details of the Enzyme-Substrate and Enzyme-Product Interaction

H. D. CORREIA; J. MARANGON; C. D. BRONDINO; J. J. G. MOURA; M.J. ROMÃO; P. J. GONZÁLEZ; T. SANTOS-SILVA

JOURNAL OF BIOLOGICAL INORGANIC CHEMISTRY

SPRINGER

Lugar: Berlin; Año: 2015 vol. 20 p. 219 - 229

0949-8257

Desulfovibrio gigas aldehyde oxidoreductase (DgAOR) is a mononuclear molybdenum-containing enzyme from the xanthine oxidase (XO) family, a group of enzymes capable of catalyzing the oxidative hydroxylation of aldehydes and heterocyclic compounds. The kinetic studies reported in this work showed that DgAOR catalyzes the oxidative hydroxylation of aromatic aldehydes, but not heterocyclic compounds. NMR spectroscopy studies using 13C labeled benzaldehyde confirmed that DgAOR catalyzes the conversion of aldehydes to the respective carboxylic acids. Steady state kinetics in solution showed that high concentrations of he aromatic aldehydes produce substrate inhibition and in the case of 3phenyl propionaldehyde a suicide substrate behavior. Hydroxylsubstituted aromatic aldehydes present none of these behaviors but the kinetic parameters are largely affected by the position of the OH group. High resolution crystallographic structures obtained from single crystals of active DgAOR soaked with benzaldehyde showed that the side chains of Phe425 and Tyr535 are important for the 14 stabilization of the substrate in the active site. On the other hand, the X-ray data of DgAOR soaked with transcinnamaldehyde showed a cinnamic acid molecule in the substrate channel.The Xray data of DgAOR soaked with 3phenyl propionaldehyde showed clearly how high substrate concentrations inactivate the enzyme by binding covalently at the surface of the enzyme and blocking the substrate channel. The different reactivity of DgAOR versus aldehyde oxidase (AO) and XO towards aromatic aldehydes and N-heterocyclic compounds is explained on the basis of the present kinetic and structural data.