[Kinetic properties of transketolase from the rat liver in a reaction with xylulose-5-phosphate and ribose-5-phosphate].
An analysis of steady-state kinetics of purified rat liver transketolase shows that the reaction proceeds according to a two-stroke substitution ("ping-pong") mechanism. Based on the kinetic data, a competitive relationship was shown to exist between xylulose-5-phosphate and ribose-5-phosphate for the sites of substrate binding by the substituted form of the enzyme with the formation of a non-productive abortive complex (kd = 125 microM). The values of constants of two monomolecular steps of the reaction (k2 = 42 s-1; k4 = 9.4 s-1) were determined. It was assumed that the maximum rate-limiting step of the transketolase reaction is the degradation of the substituted form of transketolase--ribose-5-phosphate complex having a rate constant of k4.
Gorbach
Z V
ZV
Kubyshin
V L
VL
D000818:Animals; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D010427:Pentose Phosphate Pathway; D010428:Pentosephosphates / Q000378:metabolism*; D051381:Rats; D012267:Ribosemonophosphates / Q000378:metabolism*; D013379:Substrate Specificity; D014174:Transketolase / Q000037:antagonists & inhibitors / Q000378:metabolism*
D010428:Pentosephosphates; D012267:Ribosemonophosphates; C031626:ribose-5-phosphate; C031625:xylulose-5-phosphate; D014174:Transketolase
Kineticheskie svoĭstva transketolazy pecheni krys v reaktsii s ksilulozo-5-fosfatom i ribozo-5-fosfatom.