Biochemistry (New York) 2009-07-01

Cooperative binding of substrates to transketolase from Saccharomyces cerevisiae.

I A Sevostyanova, V A Selivanov, V A Yurshev, O N Solovjeva, S V Zabrodskaya, G A Kochetov

Index: Biochemistry. (Mosc.) 74(7) , 789-92, (2009)

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Abstract

Catalytic activity of two active sites of transketolase and their affinity towards the substrates (xylulose-5-phosphate and ribose-5-phosphate) has been studied in the presence of Ca2+ and Mg2+. In the presence of Ca2+, the active sites exhibit negative cooperativity in binding both xylulose-5-phosphate (donor substrate) and ribose-5-phosphate (acceptor substrate) and positive cooperativity in the catalytic transformation of the substrates. In the presence of Mg2+, nonequivalence of the active sites is not observed.