(519a) CO2 Conversion to Methanol and Ammonia Activation of Methanol Dehydrogenase Enzyme upon Methanol Binding

Methanol Dehydrogenase (MDH) is a water soluble enzyme extracted from Methylo bacterium extroquens bacteria. MDH is able to assist in the conversion of CO2 to methanol through a series of electrochemical reactions. It then oxidizes methanol to formaldehyde in the presence of an activator (ammonia). It requires a high pH (about 9) for activity and a specific electron acceptor, cytochrome cL, although other artificial electron acceptors may be used.[1] Even though cytochrome cL is the physiological electron acceptor for MDH, the rate of its reduction in vitro is extremely slow compared with the rate measured in the artificial system with phenazine ethosulphate. The current state of the knowledge presumes that an alternative (unknown) activator operates in vivo with cytochrome cL,[2, 3] or that MDH is altered in some way during its isolation such that the ammonia is then required.[1] Hence, the study of ammonia activation upon substrate (methanol) binding helps to understand the mechanism by which the enzyme oxidizes methanol. The fact that MDH is able to assist in the methanol production process from CO2, is making this enzyme a sustainable source for the potential bioelectrochemical generation of power. In this work, the Quantum Mechanical Density Functional Theory, Molecular Mechanics and Molecular Dynamics simulations are used to study the CO2 conversion of methanol in the presence of MDH and the ammonia activation of MDH upon methanol binding in water solution. Results are presented and compared to experimental information.

1. C. Anthony, Methanol Dehydrogenase, a PQQ-Containing Quinoprotein Dehydrogenase, in SubCellular Biochemistry, Holzenburg and Scrutton, Editors. 2000, Kluwer Academic/ Plenum Publishers: New York. p. 73-118.

2. M. Dijkstra, J. Frank, and J.A. Duine, Studies on Electron Transfer from Methanol Dehydrogenase to Cytochrome cL, Biochem. J., 257. 1989. p. 87-94.

3. P.R. Afolabi, M. F., K. Amaratunga, O. Majekodunmi, S.L. Dales, R. Gill, D. Thompson, J.B. Cooper, S.P. Wood, P.M. Goodwin, and C. Anthony, Site-Directed Mutagenesis and X-Ray Crystallography of the PQQ-Containing Quinoprotein Methanol Dehydrogenase and Its Electron Acceptor, Cytochrome CL, Biochem., 40. 2001. p. 9799-9809.