tailieunhanh - Báo cáo khoa học: Revisiting the 13C-label distribution of the non-oxidative branch of the pentose phosphate pathway based upon kinetic and genetic evidence

The currently applied reaction structure in stoichiometric flux balance mod-els for the nonoxidative branch of the pentose phosphate pathway is not in accordance with the established ping-pong kinetic mechanism of the enzymes transketolase (EC ) and transaldolase (EC ). Based upon the ping-pong mechanism, the traditional reactions of the nonoxida-tive branch of the pentose phosphate pathway are replaced by metabolite specific, reversible, glycolaldehyde moiety (C2 ) and dihydroxyacetone moi-ety (C3) fragments producing and consuming half-reactions. . | iFEBS Journal Revisiting the 13C-label distribution of the non-oxidative branch of the pentose phosphate pathway based upon kinetic and genetic evidence Roelco J. Kleijn Wouter A. van Winden Walter M. van Gulik and Joseph J. Heijnen Department of Biotechnology Delft University of Technology Delft the Netherlands Keywords 13C labeling metabolic flux analysis pentose phosphate pathway transaldolase transketolase Correspondence R. J. Kleijn Department of Biotechnology Delft University of Technology Julianalaan 67 2628BC Delft the Netherlands Fax 31 15 2782355 Tel. 31 15 2785025 E-mail Website http Received 24 June 2005 accepted 8 August 2005 doi The currently applied reaction structure in stoichiometric flux balance models for the nonoxidative branch of the pentose phosphate pathway is not in accordance with the established ping-pong kinetic mechanism of the enzymes transketolase EC and transaldolase EC . Based upon the ping-pong mechanism the traditional reactions of the nonoxidative branch of the pentose phosphate pathway are replaced by metabolite specific reversible glycolaldehyde moiety C2 and dihydroxyacetone moiety C3 fragments producing and consuming half-reactions. It is shown that a stoichiometric model based upon these half-reactions is fundamentally different from the currently applied stoichiometric models with respect to the number of independent C2 and C3 fragment pools in the pentose phosphate pathway and can lead to different label distributions for 13C-tra-cer experiments. To investigate the actual impact of the new reaction structure on the estimated flux patterns within a cell mass isotopomer measurements from a previously published 13C-based metabolic flux analysis of Saccharomyces cerevisiae were used. Different flux patterns were found. From a genetic point of view it is well known that several microorganisms including Escherichia coli and S. cerevisiae .