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bioRxiv · 10.64898/2026.06.15.732455

Divergent specificity of PatA, GabT, and IlvE defines the branched transamination of Nε-carboxymethyllysine and its metabolite Nε-carboxymethylcadaverine in Escherichia coli

Vougioukas, P.·Aveta, E. F.·Hoffmann, V.·Lassak, J. M.·Hellwig, M.
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Abstract

Thermal food processing generates N{varepsilon}-carboxymethyllysine (CML), a key advanced glycation end product (AGE) and marker of the Maillard reaction in food. Escherichia coli utilizes CML as a nitrogen source. While SpeC initiates degradation by decarboxylating CML to N-carboxymethylcadaverine (CM-Cad), the enzymes liberating the nitrogen remained unknown. Here, we identify PatA, GabT, and IlvE as the glutamate-dependent transaminases responsible for CML and CM-Cad transamination. Our results reveal a branched metabolic network rather than a linear pathway: PatA shows specificity towards both substrates, while GabT and IlvE selectively process CM-Cad and CML, respectively. We further demonstrate that the carboxymethyl piperideinium ion (CM-Pip) is formed spontaneously following CM-Cad transamination and reveal the previously unknown carboxymethyl-tetrahydropicolinic acid (CM-THPA) as novel metabolite in CML metabolism. Combining molecular microbiology, biochemistry, and analytical chemistry, we demonstrate that these transaminases are essential for integrating dietary CML into bacterial nitrogen metabolism, providing a model for microbial AGE processing via underground metabolism.

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Vougioukas, P., Aveta, E. F., Hoffmann, V., Lassak, J. M., Hellwig, M.. 2026-06-16. Divergent specificity of PatA, GabT, and IlvE defines the branched transamination of Nε-carboxymethyllysine and its metabolite Nε-carboxymethylcadaverine in Escherichia coli. https://doi.org/10.64898/2026.06.15.732455

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