Figure 1

The tdc operon and the pathways for degradation of L-threonine and L-serine. Schematic representation of the organisation of the tdc operon on the chromosome of E. coli and the function of the respective gene products. (A) shows the tdc operon [15], where the tdcA and tdcR gene products are transcriptional regulators, while the tdcC gene product is L-threonine/L-serine permease [30]. Also shown are the metabolic pathways for the anaerobic degradation of (B) L-threonine and (C) L-serine, where: Ack = acetate kinase; PFL = pyruvate formate-lyase; PTA = phosphotransacetylase.