Network flux analysis: Impact of 13C-substrates on metabolism in Arabidopsis thaliana cell suspension cultures

Abstract

The aim of this study was to test the assumption that 13C-enrichment of respiratory substrate does not perturb metabolism. Cell suspension cultures of Arabidopsis thaliana were grown in MS medium containing unlabelled glucose (with 13C at natural abundance), 100% [1- 13C]glucose, 100% [U- 13C 6]glucose or 10% [U- 13C 6]glucose plus 90% unlabelled glucose. There was no significant difference in the metabolism of [U- 14C]glucose between the cultures. Similarly, the pattern of 14CO 2 release from specifically labelled [ 14C]-substrates was unaffected. Principal component analysis of 13C-decoupled 1H NMR metabolite fingerprints of cell extracts was unable to discriminate between the different culture conditions. It is concluded that 13C-enrichment of the growth substrate has no effect on flux through the central pathways of carbon metabolism in higher plants. This conclusion supports the implicit assumption in metabolic flux analysis that steady-state 13C-labelling does not perturb fluxes through the reactions of the metabolic network it seeks to quantify.