期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：45
页码：15887-15892
DOI：10.1073/pnas.0407209101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The mechanism of methanol oxidation by quinoprotein methanol dehydrogenase (MDH{middle dot}PQQ) in combination with methanol (MDH{middle dot}PQQ{middle dot}methanol) involves Glu-171[IMG]/medium/cjs0807.gif" ALT="{cjs0807}">[IMG]f1.gif" BORDER="0"> general base removal of the hydroxyl proton of methanol in concert with hydride equivalent transfer to the [IMG]/medium/15887_m01.gif" ALT="{15887_m01}"> quinone carbon of pyrroloquinoline quinone (PQQ) and rearrangement to hydroquinone (PQQH2) with release of formaldehyde. Molecular dynamics (MD) studies of the structures of MDH{middle dot}PQQ{middle dot}methanol in the presence of activator NH3 and inhibitor [IMG]f2.gif" BORDER="0"> have been carried out. In the MD structure of MDH{middle dot}PQQ{middle dot}methanol{middle dot}NH3, the hydrated NH3 resides at a distance of {approx}24 A away from methanol and the ortho-quinone portion of PQQ. As such, influence of NH3 on the oxidation reaction is not probable. We find that [IMG]f2.gif" BORDER="0"> competes with the substrate by hydrogen-bonding to Glu-171[IMG]/medium/cjs0807.gif" ALT="{cjs0807}">[IMG]f1.gif" BORDER="0"> such that the [IMG]f3.gif" BORDER="0"> complex is not reactive. Ammonia readily forms imines with quinone. Imines are present in solution as neutral [IMG]/medium/15887_m02.gif" ALT="{15887_m02}"> and protonated [IMG]/medium/15887_m03.gif" ALT="{15887_m03}"> species. MD simulations establish that the [IMG]/medium/15887_m04.gif" ALT="{15887_m04}"> derivative of [IMG]f4.gif" BORDER="0"> structure is unreactive because of the nonproductive means of methanol binding. The structure obtained by the MD simulations with the neutral [IMG]/medium/15887_m05.gif" ALT="{15887_m05}"> imine of MDH{middle dot}PQQ(NH){middle dot}methanol structure is similar to the reactive MDH{middle dot}PQQ{middle dot}methanol complex. This active site geometry allows for catalysis of hydride equivalent transfer to the [IMG]/medium/15887_m06.gif" ALT="{15887_m06}"> of PQQ(NH) by concerted Glu-171[IMG]/medium/cjs0807.gif" ALT="{cjs0807}">[IMG]f1.gif" BORDER="0"> general-base removal of the H[IMG]/medium/cjs0807.gif" ALT="{cjs0807}">OCH3 proton and Arg-324[IMG]/medium/cjs0807.gif" ALT="{cjs0807}">H+ general-acid proton transfer to the imine nitrogen. Enzyme-bound [IMG]/medium/15887_m07.gif" ALT="{15887_m07}"> derivative of PQQ [PQQ(NH)] and CH2O product are formed.
