Deciphering underground decarboxylase activity towards N_ε-modified lysine derivatives in enterobacteria

Area of Science:

• Microbiology and Gut Microbiome Research
• Biochemistry and Enzyme Function
• Dietary Compound Metabolism

Background:

• Thermal food processing creates numerous compounds that interact with the gut microbiota.
• The microbial breakdown of diet-derived Nε-modified lysine derivatives is not well understood.
• Advanced glycation end products (AGEs), such as Nε-carboxymethyllysine (CML), are abundant in processed foods.

Purpose of the Study:

• To investigate the microbial turnover of diet-borne Nε-modified lysine derivatives.
• To characterize the enzymatic activity of enterobacterial ornithine decarboxylase SpeC on CML and related compounds.
• To explore the functional implications of this metabolism for gut bacteria and potential host impacts.

Main Methods:

• Enzymatic assays to determine SpeC activity on Nε-carboxymethyllysine (CML) and other modified lysines.
• Growth experiments using Escherichia coli to assess CML utilization as a nitrogen source.
• Analysis of SpeC ortholog distribution in human gut genomes and correlation with demographic and health data.

Main Results:

• The enterobacterial enzyme SpeC degrades CML to carboxymethylcadaverine and other modified lysines into novel biogenic amines.
• SpeC enables Escherichia coli to use CML as its sole nitrogen source, enhancing survival under mild acidic conditions.
• SpeC homologs are prevalent in human gut microbiomes, with distribution patterns linked to geography, diet, and disease.

Conclusions:

• SpeC possesses promiscuous activity against various Nε-modified lysine derivatives, producing previously unidentified biogenic amines.
• This microbial metabolism of dietary compounds can influence bacterial physiology, including pH-stress adaptation in the gut.
• A potential diet-microbiome communication axis is suggested, connecting dietary chemical intake to microbial function and host health.