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)
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)
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)
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)
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)
Two substrates of the transketolase reaction are known to bind with the enzyme according to a ping-pong mechanism [1]. It is shown in this work that high concentrations of ribose-5-phosphate (acceptor substrate) compete with xylulose-5-phosphate (donor substrate), suppressing the transketolase activity (Ki = 3.8 mM). However, interacting with the(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)
Recombinant human (His)(6)-transketolase (hTK) was obtained in preparative amounts by heterologous expression of the gene encoding human transketolase in Escherichia coli cells. The enzyme, isolated in the form of a holoenzyme, was homogeneous by SDS-PAGE; a method for obtaining the apoenzyme was also developed. The amount of active transketolase in the(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)
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)