Donor Promiscuity of a Thermostable Transketolase by Directed Evolution: Efficient Complementation of 1-Deoxy-<scp>d</scp>
-xylulose-5-phosphate Synthase Activity
Enzymes catalyzing asymmetric carboligation reactions typically show very high substrate specificity for their nucleophilic donor substrate components. Structure‐guided engineering of the thermostable transketolase from Geobacillus stearothermophilus by directed in vitro evolution yielded new enzyme variants that are able to utilize pyruvate and higher aliphatic homologues as nucleophilic components
Fructose-6-phosphate aldolase immobilized on layereddoublehydroxide (FSA@LDH) has been characterized and evaluated as a biocatalyst in aldol reactions. The versatile FSA@LDH showed a comparable activity to the free FSA and can be reused several times without a notable loss of activity.
Aldolase and N-heterocyclic carbene gold(<scp>i</scp>) catalysts: compartmentalization and immobilization on anionic clays for concurrent hybrid catalysis at acidic pH
The last limitation to concurrent reactions involving hybrid catalysis, i.e. the pH, has been solved in a model hydration–aldolisation cascade towards a rare monosaccharide synthesis by mixing a NHC–gold catalyst and an aldolase. Through enzyme confinement in a cell, itself immobilised and catalysts compartmentalized, pH and catalyst incompatibilities were overcome, giving the corresponding aldol in
DXP Reductoisomerase: Reaction of the Substrate in Pieces Reveals a Catalytic Role for the Nonreacting Phosphodianion Group
作者:Svetlana A. Kholodar、Andrew S. Murkin
DOI:10.1021/bi400092n
日期:2013.4.2
The role of the nonreacting phosphodianion group of 1-deoxy-D-xylulose-5-phosphate (DXP) in catalysis by DXP reductoisomerase (DXR) was investigated for the reaction of the "substrate in pieces". The truncated substrate 1-deoxy-L-erythrulose is converted by DXR to 2-C-methylglycerol with a k(cat)/K-m that is 10(6)-fold lower than that for DXP. Phosphite dianion was found to be a nonessential activator, providing 3.2 kcal/mol of transition state stabilization for the truncated substrate. These results implicate a phosphate-driven conformational change involving loop closure over the DXR active site to generate an environment poised for catalysis.