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Background Results Conclusion Various antioxidant components have been reported in Japanese rice wine (sake), while the contribution ratio of each component to the antioxidant capacity of whole sake has not been well understood. In this study, we evaluated the radical absorption capacity (H‐ORAC and/or DPPH radical scavenging ability) and antioxidant components of commercially available sake, and estimated the major components contributing to antioxidant capacity.Water‐soluble components with a molecular weight of less than 3000 contributed more than 90% to H‐ORAC of sake by measuring the ultrafiltered fraction. The Maillard reaction seemed to have little influence on H‐ORAC by browning experiments. The radical absorption capacity of sake showed a strong positive correlation with the amounts of four antioxidant amino acids (Cys, Met, Tyr, Trp) and two phenolic acids (ferulic acid and p‐coumaric acid). Evaluating H‐ORAC of a sake model solution composed of these antioxidants revealed that the four amino acids showed a clearly higher contribution (25.7–58.2%) than the phenolic acids. In addition, there was a slight synergistic effect when the four amino acids were mixed, whereas such effects were not seen when mixed with the phenolic acids and other sake major components (organic acids, glucose and ethanol).We concluded that the contribution of free amino acids to the radical absorption capacity is quite important in sake. These findings will provide a new perspective for antioxidant researches of sake and many fermented foods. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Polyamine intake has been reported to help extend the lifespan of animals. Fermented foods contain high concentrations of polyamines, produced by fermenting bacteria. Therefore, the bacteria, isolated from fermented foods that produce large amounts of polyamines, are potentially used as a source of polyamines for humans. In this study, the strain Levilactobacillus brevis FB215, which has the ability to accumulate approximately 200 µM of putrescine in the culture supernatant, was isolated from fermented foods, specifically the Blue Stilton cheese. Furthermore, L. brevis FB215 synthesized putrescine from agmatine and ornithine, which are known polyamine precursors. When cultured in the extract of Sakekasu, a byproduct obtained during the brewing of Japanese rice wine containing high levels of both agmatine and ornithine, L. brevis FB215 grew to OD600 = 1.7 after 83 h of cultivation and accumulated high concentrations (~1 mM) of putrescine in the culture supernatant. The fermentation product also did not contain histamine or tyramine. The Sakekasu-derived ingredient fermented by the food-derived lactic acid bacteria developed in this study could contribute to increasing polyamine intake in humans. [ABSTRACT FROM AUTHOR]

The transcriptional regulator TyrR is known to undergo a dimer-to-hexamer conformational change in response to aromatic amino acids, through which it controls gene expression. In this study, we identified N316D as the second-site suppressor of Escherichia coil [TyrR.sup.E274Q], a mutant protein deficient in hexamer formation. N316 variants exhibited altered in vivo regulatory properties, and the most drastic changes were observed for [TyrR.sup.N316D] and [TyrR.sup.N316R] mutants. Gel filtration analyses revealed that the ligand-mediated oligomer formation was enhanced and diminished for [TyrR.sup.N316D] and [TyrR.sup.N316R], respectively, compared with the wild-type TyrR. ADP was substituted for ATP in the oligomer formation of [TyrR.sup.N316D].

Glutathione protects cells and organisms from oxygen species and peroxides and is indispensable for aerobically living organisms. Moreover, it acts against xenobiotics and drugs by the formation and excretion of glutathione S conjugates. In this study, we show that the yliA, -B, -C, and -D genes of Escherichia coli K-12 encode a glutathione transporter with the ATP-binding cassette. The transporter imports extracellular glutathione into the cytoplasm in an ATP-dependent manner. This transporter, along with [gamma]-glutamyltranspeptidase, has an important role in E. coli growth with glutathione as a sole sulfur source.

In Escherichia coli, the active transport of phenylalanine is considered to be performed by two different systems, AroP and PheP. However, a low level of accumulation of phenylalanine was observed in an aromatic amino acid transporter-deficient E. coli strain ([DELTA]aroP [DELTA]pheP [DELTA]mtr [DELTA]tna [DELTA]tyrP). The uptake of phenylalanine by this strain was significantly inhibited in the presence of branched-chain amino acids. Genetic analysis and transport studies revealed that the LIV-I/LS system, which is a branched-chain amino acid transporter consisting of two periplasmic binding proteins, the LIV-binding protein (LIV-I system) and LS-binding protein (LS system), and membrane components, LivHMGF, is involved in phenylalanine accumulation in E. coli cells. The [K.sub.m] values for phenylalanine in the LIV-I and LS systems were determined to be 19 and 30 [micro]M, respectively. Competitive inhibition of phenylalanine uptake by isoleucine, leucine, and valine was observed for the LIV-I system and, surprisingly, also for the LS system, which has been assumed to be leucine specific on the basis of the results of binding studies with the purified LS-binding protein. We found that the LS system is capable of transporting isoleucine and valine with affinity comparable to that for leucine and that the LIV-I system is able to transport tyrosine with affinity lower than that seen with other substrates. The physiological importance of the LIV-ULS system for phenylalanine accumulation was revealed in the growth of phenylalanine-auxotrophic E. coli strains under various conditions.

Results reveal that the tutB gene from Erwinia herbicola, though possesses high sequence similarity to tryptophan transporter gene, encodes tyrosine-specific transporter protein. Data indicate that tryptophanase operon, the tpl, and tutB gene do not form an operon despite the latters localization just downstream of tpl.

Researchers have created a mutant form of the enzyme tyrosine phenol-lyase from Erwinia herbicola that does not require L-tyrosine. This bacterium is used to produce L-DOPA for the treatment of Parkinson's disease, but the wild enzyme requires tyrosine. The tyrosine must then be separated from L-DOPA.