Effect of bivalent cations on the interaction of transketolase with its donor substrate.
The effect of the type of the cation cofactor of transketolase (i.e., Ca2+ or Mg2+) on its interaction with xylulose 5-phosphate (donor substrate) has been studied. In the presence of magnesium, the active centers of the enzyme were functionally equivalent with respect to xylulose 5-phosphate binding and exhibited identical affinities for the donor substrate. Substitution of Ca2+ for Mg2+ results in the loss of the equivalence. In particular, this becomes apparent on binding of xylulose 5-phosphates to one of the two active centers of the enzyme, which caused the second center to undergo a several fold decrease in the affinity for the donor substrate.
Sevostyanova
Irina A
IA
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia.
Yurshev
Vladimir A
VA
Solovjeva
Olga N
ON
Zabrodskaya
Svetlana V
SV
Kochetov
German A
GA
D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D010428:Pentosephosphates / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D014174:Transketolase / Q000187:drug effects / Q000378:metabolism*
D002413:Cations, Divalent; D010428:Pentosephosphates; C031625:xylulose-5-phosphate; D014174:Transketolase; D008274:Magnesium; D002118:Calcium