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Biochemical Effects in Animals
Published in Stephen P. Coburn, The Chemistry and Metabolism of 4′-Deoxypyridoxine, 2018
In other studies relating to the tryptophan-niacin pathway, Umbreit and Waddell522 noted that deoxypyridoxine at concentrations up to 900 pg/mf showed no effect on tryptophanase from Escherichia coli. Kawakita et al.234 also reported that deoxypyridoxine phosphate:pyridoxal phosphate ratios as high as 1000 had no effect on that enzyme.
The Modification of Methionine
Published in Roger L. Lundblad, Chemical Reagents for Protein Modification, 2020
Oxidation of methionine to methionine sulfoxide (Figure 2) can occur under a variety of conditions. Reagents for the “selective” oxidation of methionine which have attracted recent attention include chloramine T2,3 (0.1 M phosphate, pH 7.0 or 0.1 M Tris, pH 8.4), sodium periodate3 (0.1 M sodium acetate, pH 5.0), and hydrogen peroxide.4 The reaction of methionine with chloramine T can be followed spectrophotometrically.2 The reaction of chloramine T with methionine (Figure 3) results in a significant change in the spectrum of chloramine T as shown in Figure 4. The use of this spectral change in the determination of methionine is shown in Figure 5. Cysteine interfered with this determination but other amino acids (i.e., tyrosine, tryptophan, histidine, serine) did not have any effect on the accuracy of analysis for methionine. It is noted that the oxidation of methionine is a possible side-reaction of the treatment of proteins with N-bromosuccinimide.5 Oda and Tokushige1 have studied the oxidation of tryptophanyl residues in tryptophanase by chloramine T. When the native enzyme is treated with chloroamine T (20 mM potassium phosphate, pH 8.5, 0°C), sulfhydryl groups and methionine residues are oxidized with loss of catalytic activity. With prior modification of the sulfhydryl groups with 5,5’-dithiobis(2-nitrobenzoic acid), 4-5/16 methionyl residues are modified with further loss of catalytic activity. In an earlier study, Sakurai and Nagahara6 compared the relative sensitivity of amino acids in epsilon toxin to oxidation by N-bromosuccinimide (pH 5.0, 0.05 M acetate), N-chlorosuccinimide (pH 8.5, 0.05 M Tris) and chloramine T (pH 8.5, 0.05 M Tris). Methionine was totally lost with both chloramine T and N-chlorosuccinimide but 21 % remained in the N-bromosuccinimidetreated sample. The opposite was found for tryptophan with total loss with either N-bromosuccinimide or N-chlorosuccinimide but no loss with chloramine T.
Indole intercepts the communication between enteropathogenic E. coli and Vibrio cholerae
Published in Gut Microbes, 2022
Orna Gorelik, Alona Rogad, Lara Holoidovsky, Michael M. Meijler, Neta Sal-Man
EPEC and V. cholera co-infections occur in the small intestine,17 which is colonized by a diverse population of microorganisms collectively referred to as the microbiome.18,19 The gut microbiome regulates diverse physiological processes, such as food digestion and metabolite production, the maintenance of the gut mucosal barrier, and the prevention of pathogenic invasion.18–22 Microbiome-derived metabolites are essential for the regulation of the intestinal immune system and the maintenance of the gut microbiome homeostasis,23–26 thereby shaping human health and disease.27–29 In this study, we focused on indole, an amino-acid-derived metabolite produced from the degradation of tryptophan by a tryptophanase enzyme encoded by the tnaA gene mainly in commensal bacteria such as Bacteroides thetaiotaomicron.23,25,26 Indole concentrations are estimated to range as high as 1 mM in the human gastrointestinal tract.25,30 These high indole concentrations have been shown to decrease enterohemorrhagic E. coli (EHEC) motility, biofilm formation, adherence to epithelial cells, and virulence gene expression, in addition to enhancing drug resistance of Salmonella enterica.25,31–33
Gut associated metabolites and their roles in Clostridioides difficile pathogenesis
Published in Gut Microbes, 2022
Andrea Martinez Aguirre, Joseph A. Sorg
Finally, indole may play a role during C. difficile infections. Supernatant from C. difficile stationary phase cultures can induce the expression of tryptophanase (tnaA) in E. coli. The levels of indole increased in other indole-producing microbes in the gut (e.g., L. reuteri and E. faecalis) in co-culturing assays with C. difficile. Interestingly, the MIC (5 mM) of C. difficile strains were found to be higher than the MIC of multiple gastrointestinal bacteria tested, ranging from 2–4 mM. These results led the authors to the hypothesis that the ability of C. difficile to resist higher gut indole concentrations may provide the bacterium a competitive advantage.96 Importantly, these experiments were performed under in vitro conditions and future work with animal models is needed to test the proposed hypothesis.
Molecules involved in motility regulation in Escherichia coli cells: a review
Published in Biofouling, 2020
Fazlurrahman Khan, Nazia Tabassum, Dung Thuy Nguyen Pham, Sandra Folarin Oloketuyi, Young-Mog Kim
Non-pathogenic microorganisms use several protective mechanisms against pathogenic microorganisms, including the production and secretion of antimicrobial molecules into their environment (Chu et al. 2012; Abt and Pamer 2014; Fang et al. 2018). Among such molecules, the most studied are indole and its derivatives, which were found to be potent antibiofilm and antivirulence agents against E. coli (Lee et al. 2012; Lee et al. 2015). Indole is derived from tryptophan by the action of bacterial tryptophanase. Indole and its derivatives such as 7-hydroxyindole (from Acinetobacter calcoaceticus strain 4-1-5) were found to attenuate the swimming property of E. coli (Lee et al. 2007; Lee et al. 2013). Similarly, brominated furanones such as (5Z)-4-bromo-5-(bromomethylene)-3-butyl-2(5H)-furanone isolated from red algae (Delisea pulchra) were found to suppress E. coli swarming (Ren et al. 2001).