Ludmilla E. Meshalkina

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Data from site-directed mutagenesis and X-ray crystallography show that His103 of holotransketolase (holoTK) does not come into contact with thiamin diphosphate (ThDP) but stabilizes the transketolase (TK) reaction intermediate, alpha,beta-dihydroxyethyl-thiamin diphosphate, by forming a hydrogen bond with the oxygen of its beta-hydroxyethyl group [Eur. J.(More)
A computer model of the spatial structure of transketolase-like protein (TKTL1), a marker of certain tumor tissues, has been constructed using the known spatial structure of transketolase found in normal human tissues. The structure of the two proteins at all levels of their organization has also been compared. On the basis of the revealed differences in(More)
Until recently it was assumed that the transketolase-like protein (TKTL1) detected in the tumor tissue, is catalytically active mutant form of human transketolase (hTKT). Human TKT shares 61% sequence identity with TKTL1. And the two proteins are 77% homologous at the amino acid level. The major difference is the absence of 38 amino acid residues in the(More)
The influence of substrates on the interaction of apotransketolase with thiamin diphosphate was investigated in the presence of magnesium ions. It was shown that the donor substrates, but not the acceptor substrates, enhance the affinity of the coenzyme either to only one active center of transketolase or to both active centers, but to different degrees in(More)
Apart from catalyzing the common two-substrate reaction with ketose as donor substrate and aldose as acceptor substrate, transketolase is also able to catalyze a one-substrate reaction utilizing only ketose (xylulose 5-phosphate) as substrate. The products of this one-substrate reaction were glyceraldehyde 3-phosphate and erythrulose. No free glycolaldehyde(More)
MOTIVATION Addition of labeled substrates and the measurement of the subsequent distribution of the labels in isotopomers in reaction networks provide a unique method for assessing metabolic fluxes in whole cells. However, owing to insufficiency of information, attempts to quantify the fluxes often yield multiple possible sets of solutions that are(More)
Transketolase from Saccharomyces cerevisiae exhibits a rarely reported activity with a methylated analogue of the native cofactor, 4'-methylamino-thiamin diphosphate. We demonstrated the kinetic stability of the dihydroxyethyl carbanion/enamine intermediate to be dependent on the functionality of the 4'-aminopyrimidine moiety of thiamin diphosphate [R.(More)
A kinetic model of bisubstrate reaction catalyzed by baker's yeast transketolase is proposed. The model considers individual stages of substrates reversible primary binding. The model corresponds to the observed kinetics of product accumulation within a wide range of initial substrate concentrations. Kinetic parameters for the best simulation of the(More)
Direct determination of the number of catalytically active molecules of the coenzyme in holotransketolase (sedoheptulose-7-phosphate:D-glyceraldehyde-3-phosphate glycoaldehydetransferase, EC 2.2.1.1) has corroborated our previous data indicating that in the native enzyme there are two active centres. They have been provided to be functionally identical. It(More)
Transketolase from baker's yeast is a thiamin diphosphate-dependent enzyme in sugar metabolism that reconstitutes with various analogues of the coenzyme. The methylated analogues (4'-methylamino-thiamin diphosphate and N1'-methylated thiamin diphosphate) of the native cofactor were used to investigate the function of the aminopyrimidine moiety of the(More)