SummaryMocR/GabR family proteins are widely distributed prokaryotic transcriptional regulators containing pyridoxal 5′-phosphate (PLP), a coenzyme form of vitamin B6. The Bacillus subtilis GabR, probably the most extensively studied MocR/GabR family protein, consists of an N-terminal DNA-binding domain and a PLP-binding C-terminal domain that has a structure homologous to aminotransferases. GabR suppresses transcription of gabR and activates transcription of gabT and gabD, which encode γ-aminobutyrate (GΑΒΑ) aminotransferase and succinate semialdehyde dehydrogenase, respectively, in the presence of PLP and GABA. In this study, we examined the mechanism underlying GabR-mediated gabTD transcription with spectroscopic, crystallographic and thermodynamic studies, focusing on the function of the aminotransferase domain. Spectroscopic studies revealed that GABA forms an external aldimine with the PLP in the aminotransferase domain. Isothermal calorimetry demonstrated that two GabR molecules bind to the 51-bp DNA fragment that contains the GabR-binding region. GABA minimally affected ΔG binding upon binding of GabR to the DNA fragment but greatly affected the contributions of ΔH and ΔS to ΔGbinding. GABA forms an external aldimine with PLP and causes a conformational change in the aminotransferase domain, and this change likely rearranges GabR binding to the promoter and thus activates gabTD transcription.

Background Outpatient cancer chemotherapy may lead to improved quality of life (QOL) by allowing treatment to continue without impairing the social lives of patients compared with hospitalization. However, the occurrence of serious adverse events may cause a decline in QOL. We investigated the relationship between outpatient chemotherapy-induced adverse events and QOL. Methods A single-center retrospective descriptive study was conducted in patients who received outpatient chemotherapy at Gifu University Hospital (Gifu, Japan) between September 2017 and December 2018. The utility values of QOL, type and severity of adverse events, type of cancer, chemotherapy regimen, and other patient demographics were analyzed. Adverse events were graded according to the Common Terminology Criteria for Adverse Events, version 4.0. QOL was evaluated using the Japanese version of the EuroQol 5 Dimension 5 Level (EQ-5D-5L). Associations between the EQ-5D-5L utility value and serious adverse events were assessed using adjusted (age and sex) odds ratios obtained with a proportional odds logistic regression model. Results Data from 1008 patients who received 4695 chemotherapy cycles were analyzed. According to proportional odds logistic regression, the adverse events that significantly correlated with a decreased EQ-5D-5L utility value were malaise, edema of the limbs, peripheral neuropathy, pruritus, and dry skin. Based on the proportional odds logistic analysis, neither cancer type nor anticancer drugs were significantly correlated with the EQ-5D-5L utility value in patients who received chemotherapy. Pharmaceutical care for peripheral neuropathy significantly improved patients' EQ-5D-5L utility value from 0.747 to 0.776 (P < 0.01). Conclusions Adverse events (i.e., peripheral neuropathy, malaise, and edema of the limbs) are significantly correlated with a decrease in QOL, regardless of the type of cancer or anticancer drugs used. Pharmaceutical care provided by pharmacists in collaboration with physicians may improve QOL.

Bacillus subtilis GabR is a transcriptional regulator consisting of a helix-turn-helix N-terminal DNA-binding domain, a pyridoxal 5'-phosphate (PLP)-binding C-terminal domain that has a structure homologous to aminotransferases, and a linker of 29 amino acid residues. In the presence of γ-aminobutyrate (GABA), GabR activates the transcription of gabT and gabD, which encode GABA aminotransferase and succinate semialdehyde dehydrogenase, respectively. We expressed N-terminal and C-terminal domain fragments (named N'-GabR and C'-GabR) in Escherichia coli cells, and obtained N'-GabR as a soluble monomer and C'-GabR as a soluble dimer. Spectroscopic studies suggested that C'-GabR contains PLP and binds to d-Ala, β-Ala, d-Asn and d-Gln, as well as GABA, although the intact GabR binds only to GABA. N'-GabR does not bind to the DNA fragment containing the GabR-binding sequence regardless of the presence or absence of C'-GabR. A fusion protein consisting of N'-GabR and 2-aminoadipate aminotransferase of Thermus thermophilus bound to the DNA fragment. These results suggested that each domain of GabR could be an independent folding unit. The C-terminal domain provides the N-terminal domain with DNA-binding ability via dimerization. The N-terminal domain controls the ligand specificity of the C-terminal domain. Connection by the linker is indispensable for the mutual interaction of the domains.

Roasting of green tea causes oligomerization of tea catechins, which decreases the astringency. The aim of this study was to elucidate the oligomerization mechanism. The 13 C NMR spectrum of the oligomer fraction showed signals arising from catechin and sugar residues. Heating of epigallocatechin-3-O-gallate with 13 C-labeled glucose (150°C for 2 h) suggested that condensation of sugars with catechin A-rings caused the oligomerization. The dimeric product obtained by heating for a shorter period (30 min) suggested cross-linking occurred between sugars and catechin A-rings. Furthermore, heating of phloroglucinol, a catechin A-ring mimic, with glucose, methylglyoxal, and dihydroxyacetone, confirmed that the basic mechanism included reaction of the catechin A-ring methine carbons with carbonyl carbons of glucose and their pyrolysis products.

Theacitrins A-C are yellow pigments of black tea that are produced by oxidative coupling of gallocatechins, i.e., flavan-3-ols with pyrogallol-type B-rings. However, their stereostructures have not yet been determined. In this study, DFT calculations of NMR chemical shifts of theacitrin C (1) and TDDFT calculations of the ECD spectra of theacitrinin A (5), a degradation product of theacitrin C (1), were used to determine the stereostructure of the theacitrins. Furthermore, the preparation of theacitrins A (4) and C (1) by enzymatic oxidation of an epigallocatechin (7) and epigallocatechin-3-O-gallate (2) mixture confirmed their structural relationship.