Transcriptional regulation of theN_ε-fructoselysine metabolism inEscherichia coliby global and substrate-specific cues

Abstract

Thermally processed food is an important part of the human diet. Heat-treatment, however, promotes the formation of so-called Amadori rearrangement products (ARPs), such as fructoselysine. The gut microbiota including Escherichia coli can utilize these compounds as a nutrient source. While the degradation route for fructoselysine is well described, regulation of the corresponding pathway genes frlABCD remained poorly understood. Here we use bioinformatics combined with molecular and biochemical analyses and show that in E. coli, fructoselysine metabolism is tightly controlled at the transcriptional level. The global regulator Crp (CAP), as well as the alternative sigma factor σ32 (RpoH) contribute to promoter activation at high cAMP-levels and heat stress, respectively. In addition, we identified and characterized a transcriptional regulator FrlR, encoded adjacent to frlABCD, as fructoselysine-6-phosphate specific roadblock repressor. Our study provides profound evidence that the interplay of global and substrate-specific regulation is a perfect adaptation strategy to efficiently utilize unusual substrates within the human gut environment.Abbreviated SummaryThermal food processing promotes the formation of Amadori rearrangement products (ARPs), such as fructoselysine. The gut microbiota including Escherichia coli can utilize these compounds as a nutrient source. We show that in E. coli, fructoselysine metabolism is tightly controlled at the transcriptional level by global and substrate-specific regulators. Their interplay is a perfect adaptation strategy to efficiently utilize fructoselysine within the human gut environment.Graphical Abstract

Identification of Pseudomonas asiatica subsp. bavariensis str. JM1 as the first Nε‐carboxy(m)ethyllysine‐degrading soil bacterium

“…It is a specific case of the common amino‐carbonyl reactions and mainly refers to the reaction of reducing sugars and their degradation products with amino and guanidino compounds (Ulrich and Cerami, 2001). First, Schiff bases are formed at the amino termini of free amino acids, peptides, or proteins, or the ε‐amino groups of lysine residues (Hellwig and Henle, 2014; Graf von Armansperg et al ., 2021). These Schiff bases rearrange very fast into the more stable Amadori or Heyns products (Heyns and Noack, 1962).…”