Unified Theory of Bacterial Sialometabolism: How and Why Bacteria Metabolize Host Sialic Acids

Figure 5

Canonical N-acylneuraminate (nan) dissimilatory pathway for metabolism of Neu5Ac by E. coli. Colored arrows indicate relative transcriptional directions and functions of genes involved in converting Neu5Ac to GlcNAc-6-P after transport of exogenous sialic acid by the permease, NanT (yellow): aldolase or lyase (blue), epimerase (green), kinase (purple), yhcH (orange). Expression of the structural genes of this operon are regulated by the repressor, NanR (red) located immediately upstream of the nanA start site. Depending on the bacterial species, NagA or NagB may be part of the canonical operon or, as in the case of E. coli, located in a separate operon.