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Cooperative Binding of Substrates to Transketolase from Saccharomyces cerevisiae

I. A. Sevostyanova1, V. A. Selivanov2, V. A. Yurshev3, O. N. Solovjeva1, S. V. Zabrodskaya4, and G. A. Kochetov1*

1Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-3181; E-mail: kochetov@belozersky.msu.ru

2Barcelona University, Barcelona 08028, Spain

3Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-4195

4Institute of Biochemistry, National Academy of Sciences of Belarus, Bulvar Leninskogo Komsomola 50, 230017 Grodno, Belarus; fax: (0152) 43-4161

* To whom correspondence should be addressed.

Received July 17, 2008; Revision received October 6, 2008
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.
KEY WORDS: transketolase, nonequivalence of active sites, bivalent cations, xylulose-5-phosphate, ribose-5-phosphate

DOI: 10.1134/S0006297909070128