NAD+-specific D-arabinose dehydrogenase and its contribution to erythroascorbic acid production in Saccharomyces cerevisiae

Erythroascorbic acid (eAsA) is a five-carbon analog of ascorbic acid, and it is synthesized from D-arabinose by D-arabinose dehydrogenase (ARA) and D-arabinono-gamma-lactone oxidase. We found an NAD+-specific ARA activity which is operative under submillimolar level of d-arabinose in the extracts of Saccharomyces cerevisiae. The hypothetical protein encoded by YMR041c showed a significant homology to a l-galactose dehydrogenase which plays in plant ascorbic acid biosynthesis, and we named it as Ara2p. Recombinant Ara2p showed NAD+-specific ARA activity with Km=0.78 mM to d-arabinose, which is 200-fold lower than that for the conventional NADP+-specific ARA, Ara1p. Gene disruptant of ARA2 lost entire NAD+-specific ARA activity and the conspicuous increase in intracellular eAsA by exogenous d-arabinose feeding, while the double knockout mutant of ARA1 and ARA2 still retained measurable amount of eAsA. It demonstrates that Ara2p, not Ara1p, mainly contributes to the production of eAsA from d-arabinose in S. cerevisiae.     

A single nucleotide polymorphism in NF-κB inducing kinase is associated with mortality in septic shock

We tested the hypothesis that single nucleotide polymorphisms (SNPs) within genes of the NF-κB pathway are associated with altered clinical outcome of septic shock patients. We genotyped 59 SNPs in the NF-κB pathway in a discovery cohort of septic shock patients (St. Paul's Hospital [SPH], N = 589), which identified the C allele of rs7222094 T/C within MAP3K14 (NF-κB inducing kinase; NIK) associated with increased 28-d mortality (uncorrected p = 0.00024, Bonferroni corrected p = 0.014). This result was replicated in a second cohort of septic shock patients (Vasopressin and Septic Shock Trial [VASST; N = 616]) in which the CC genotype of rs7222094 was associated with increased 28-d mortality (Cox regression: SPH cohort hazard ratio [HR], 1.35; 95% confidence interval [CI], 1.12-1.64; p = 0.002 Caucasian only; and VASST cohort HR, 1.24; 95% CI, 1.00-1.52; p = 0.048 Caucasian only). Patients having the CC genotype of rs7222094 in SPH experienced more renal and hematological dysfunction (p = 0.003 and p = 0.011), while patients of the VASST cohort with the rs7222094 CC genotype showed the same trend toward more renal dysfunction. In lymphoblastoid cell lines, we found the rs7222094 genotype most strongly associated with mRNA expression of CXCL10, a chemokine regulated by NF-κB. Accordingly, we measured CXCL10 protein levels and found that the CC genotype of rs7222094 was associated with significantly lower levels than those of the TT genotype in lymphoblastoid cell lines (p < 0.05) and in septic shock patients (p = 0.017). This suggests that the CC genotype of NIK rs7222094 is associated with increased mortality and organ dysfunction in septic shock patients, perhaps due to altered regulation of NF-κB pathway genes, including CXCL10.     

Outcome prediction in sepsis combined use of genetic polymorphisms - A study in Japanese population

Genetic polymorphisms have recently been found to be related to clinical outcome in septic patients. The present study investigated to evaluate the influence of genetic polymorphisms in Japanese septic patients on clinical outcome and whether use of genetic polymorphisms as predictors would enable more accurate prediction of outcome. Effects of 16 genetic polymorphisms related to pro-inflammatory mediators and conventional demographic/clinical parameters (age, sex, past medical history, and APACHE II score) on ICU mortality as well as disease severity during ICU stay were examined in the septic patients (n=123) admitted to the ICU between October 2001 and November 2007 by multivariable logistic regression analysis. ICU mortality was significantly associated with TNF -308GA, IL1β -31CT/TT, and APACHE II score. Receiver-operating characteristics (ROC) analysis demonstrated that, compared with APACHE II score alone (ROC-AUC=0.68), use of APACHE II score and two genetic parameters (TNF -308 and IL1β -31) enabled more accurate prediction of ICU mortality (ROC-AUC=0.80). Significant association of two genetic polymorphisms, TNF -308 and IL1β -31, with ICU mortality was observed in septic patients. In addition, combined use of these genetic parameters with APACHE II score may enable more accurate prediction of outcome in septic patients.     

The role of light in formation of modified S2-state upon low pH-treatment of oxygen-evolving Photosystem II

An abnormal, structurally modified, kinetically stable S₂-state has been reported to be induced when Photosystem II was treated with NaCl-EGTA (or EDTA) in the light or with pH in darkness, both are assumed to release functional Ca²⁺. In order to compare the mechanism of induction of modified S₂-state between the two treatments, effects of illumination during or before low pH-treatment on formation of the abnormal S₂-state were investigated by means of thermoluminescence measurements and low temperature EPR spectroscopy. Following results have been obtained: Flash illumination during low pH-treatment did not practically induce the abnormal S₂-state, whereas preflash illumination given immediately before low pH-treatment efficiently induced the abnormal S₂-state, and its amplitude showed a period-four oscillation on varying the preflash number with maxima at the second and sixth flashes. The abnormal S₂-state thus induced by preflashes was identical with the modified S₂-state that could be induced in dark-low pH-treated Photosystem II by excitation at 0°C after neutralization to pH 6.5. It was inferred that in low pH-treatment, modified S₂-state can be formed from both S₂- and S₃-states, but its yield from the latter is much higher than from the former, consistent with the early results by Boussac et al. obtained for NaCl-EGTA-light or NaCl-citrate-light treatment.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - EDTA ethylenediaminetetraactate - EGTA ethylene glycol bis(-aminoethylether)-N,N,N,N-tetraacetic acid - Mes 2-(N-morpholino)ethanesulfonic acid - PS II Photosystem II     

Functional Comparison of d-Serine and Glycine in Rodents: The Effect on Cloned NMDA Receptors and the Extracellular Concentration

Abstract: We compared the activity of free d -Ser on the potentiation of cloned NMDA receptors with that of Gly by using a Xenopus oocyte expression system. The extracellular concentration of free d -Ser and Gly was further studied by means of microdialysis. The ED₅₀ values of d -Ser were three to four times lower than those of Gly in any combination of ε1, ε2, ε3, or ε4 and ζ1. Site-directed mutagenesis of ζ1 subunits revealed that some aromatic residues necessary for the action of Gly affected the ED₅₀ value of d -Ser. This result showed that the residues play crucial roles in the action of d -Ser. In vivo microdialysis of rodent brain revealed that the extracellular concentration of free d -Ser in the frontal cortex (6.5 µ M ) was high enough to saturate the Gly site on the NMDA receptor, but that in the cerebellum was not. These findings suggest that d -Ser is a candidate of the endogenous potentiator of the NMDA receptor in the rodent frontal cortex.     

The electromotive force of the Chara membrane during the hyperpolarizing response

The hyperpolarizing response of the Chara internodal cell wasstudied by applying the voltage clamp and constant current techniques.By assuming the membrane as an electromotive force (emf) inseries with a resistance r (which is the sum of a series resistancer_s and the membrane resistance r_m), it was shown that the hyperpolarizingresponse was brought about not only by the increase in membraneresistance but by the increase in membrane emf. The time dependentcurrent-voltage (I–V_m) curve obtained under the voltageclamp during the hyperpolarizing response showed a negativeresistance. The hyperpolarizing response is also an excitation,since it is a transition process of the membrane across a negativeresistance region. (Received July 22, 1974; )