title: Effect of bivalent cations on the interaction of transketolase with its donor substrate.
abstract: 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.
authors.affiliation: A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia.
authors.forename: Irina A
authors.initials: IA
authors.lastname: Sevostyanova
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Yurshev
authors.forename: Olga N
authors.initials: ON
authors.lastname: Solovjeva
authors.forename: Svetlana V
authors.initials: SV
authors.lastname: Zabrodskaya
authors.forename: German A
authors.initials: GA
authors.lastname: Kochetov
mesh_terms: 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*
chemical_list: D002413:Cations, Divalent; D010428:Pentosephosphates; C031625:xylulose-5-phosphate; D014174:Transketolase; D008274:Magnesium; D002118:Calcium