El-Mansi, Mansi (2005) Free-CoA mediated regulation of intermediary and central metabolism: An hypothesis, which accounts for the excretion of α-ketoglutarate during aerobic growth of E. coli on acetate. Research in Microbiology, 156 (8). pp. 874-879. ISSN 0923 2508

Abstract/Description

During growth of Escherichia coli on acetate, phosphotransacetylase and -ketoglutarate dehydrogenase are in direct competition for their common co-factor, HS-CoA. Such competition is resolved in favour of phosphotransacetylase, thus rendering -ketoglutarate dehydrogenase rate-limiting (controlling) and, in turn, creating a bottleneck at the level of -ketoglutarate in the Krebs cycle. Accumulation of -ketoglutarate is then balanced by its excretion. Addition of pyruvate, glucose or any glycolytic intermediate to acetate-grown culture relieves such a bottleneck by reversing carbon flow through phosphotransacetylase to give acetyl phosphate and much-needed HS-CoA. The urgent need for HS-CoA by the primordial organism might therefore have provided the selective pressure that led to the co-evolution of phosphotransacetylase and the two-malate synthase isoenzymes.

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