Mechanism of mycolic acid cyclopropane synthase: A theoretical study
2011 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 50, no 9, 1505-1513 p.Article in journal (Refereed) Published
The reaction mechanism of mycolic acid cyclopropane synthase is investigated using hybrid density functional theory. The direct methylation mechanism is examined with a large model of the active site constructed on the basis of the crystal structure of the native enzyme. The important active site residue Glu140 is modeled in both ionized and neutral forms. We demonstrate that the reaction starts via the transfer of a methyl to the substrate double bond, followed by the transfer of a proton from the methyl cation to the bicarbonate present in the active site. The first step is calculated to be rate-limiting, in agreement with experimental kinetic results. The protonation state of Glu140 has a rather weak influence on the reaction energetics. In addition to the natural reaction, a possible side reaction, namely a carbocation rearrangement, is also considered and is shown to have a low barrier. Finally, the energetics for the sulfur ylide proposal, which has already been ruled out, is also estimated, showing a large energetic penalty for ylide formation.
Place, publisher, year, edition, pages
American Chemical Society , 2011. Vol. 50, no 9, 1505-1513 p.
IdentifiersURN: urn:nbn:se:su:diva-43040DOI: 10.1021/bi101493pOAI: oai:DiVA.org:su-43040DiVA: diva2:353213
FunderSwedish Research Council