engleski

Catalysis by Mutants of Methylmalonyl-CoA Mutase: A Theoretical Rationalization for a Change in the Rate-Determining Step

Removal of the histidine‐244 moiety of methylmalonyl‐CoA mutase changes the rate‐determining step of the coenzyme‐B12 mediated reaction: Ab initio calculations support the view that while the rate‐limiting step in the mutant enzyme is a rearrangement, that in the wild‐type enzyme has a greater contribution from the hydrogen abstraction required to form the product. The energy barrier to rearrangement in the latter case is reduced by partial proton transfer, as is evident in the crystal stucture which shows His 244 ideally positioned to donate a hydrogen bond to the carbonyl oxygen atom of the ester (see picture).

Catalysis ; Methylmalonyl-CoA Mutase ; B12

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