The enzyme that catalyzes the committed step in pyrimidine biosynthesis, aspartate transcarbamoylase, has been compared in selected endospore-forming organisms and in morphologically similar control organisms. The ATCases and pyrimidine salvage from Sporosarcina ureae, Sporolactobacillus inulinus, Lactobacillus fermentum, and Micrococcus luteus were compared to those of Bacillus subtilis. While the ATCases from Sporosarcina ureae, Sporolactobacillus inulinus, and L. fermentum were found to exhibit characteristics to that of Bacillus with respect to molecular weight and kinetics, M. luteus ATCase was larger at approximately 480 kDa. Furthermore, pyrimidine salvage in Sporosarcina ureae and M. luteus was identical to those of B. subtilis, while pyrimidine salvage of Sporolactobacillus inulinus and L. fermentum resembled that of the pseudomonads.

Aim: To evaluate the association between elevated serum transaminase levels and insulin resistance (IR) in a population of healthy individuals. Methods: We define IR with a cut-off point of homeostatic model assessment (HOMA-IR) ≥ 3.8. For aspartate aminotransferase (AST), we consider elevated values >30 U/L in women and values >36 U/L in men. For alanine aminotransferase (ALT), we consider elevated values >30 U/L in women and values >40 U/L in men. We performed a crude and adjusted generalized linear model from Poisson family with robust variance, in order to evaluate the association between elevated serum transaminase levels and IR. The associations were presented as prevalence ratio (PR) with their respective 95% confidence intervals (95% CI). Results: We included 261 participants in the study. The median age was 39 years (31–45) and 23.7% of the participants were men. The prevalence of elevated serum transaminase for AST and ALT were, 13.8% and 26.1%, respectively. The prevalence of IR was 34.1%. In the crude analysis we found statistical significance between elevated AST and ALT with IR (PR = 3.18; 95% CI: 2.33–4.34 and PR = 2.44; 95% CI: 1.88–3.30; respectively). However, in the multivariate analysis, the association only remained statistically significance with ALT, but lost its significance with AST, PR = 1.90; CI 95%: 1.31–2.77 and a PR = 1.23; CI 95%: 0.93–1.61; respectively. Conclusion: Elevated serum levels of ALT were associated with insulin resistance. ALT could be used in clinical practice as an additional tool to assess IR in apparently healthy people. / Dirección de Gestión de la Investigación, Universidad de Antofagasta / Revisión por pares

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18304号 / 工博第3896号 / 新制||工||1598(附属図書館) / 31162 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 跡見 晴幸, 教授 森 泰生, 教授 濵地 格 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

The effects of spermine, an endogenous polyamine, were examined in area CA1 of the rat hippocampal slice preparation. Spermine, at low millimolar concentrations, rapidly and potently depressed NMDA and K/AMPA-mediated population EPSPs, and GABA-mediated monosynaptic population IPSPs. These effects contrast with its well-known potentiation of NMDA currents at lower concentrations. Our results raise the possibility that the large intracellular stores of spermine that are released after various neural insults could act as an endogenous neuroprotective mechanism by limiting excessive calcium entry.

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No description available.

The carbamoyl region of the active site of aspartate transcarbamoylase from Escherichia coli was probed using an enzyme assay in which the two substrates were varied near their respective K_m 's. The inhibitors tested, some synthesized and some commercially available, were chosen to satisfy the structural requirements for binding to either the dicarboxylate or phosphate region with a substituent capable of extending into the carbamoyl region. However, the dicarboxylate based inhibitors were found to bind in an abnormal manner (unlike L-aspartate or succinate on which they were based). The carbamoyl region was found to contain a positively charged side-chain and preliminary results indicate that tetrahedral groups are not preferred over trigonal moieties. It is suggested that electrostatic stabilization of the negative charge which develops in the transition state may be a major factor in promoting catalysis. The identity of this charged group in the carbamoyl region is postulated to be His134 based on available X-ray diffraction data. The binding subsites of the active site of this enzyme were also found to be oriented in essentially the same plane. These results will greatly aid in the design of future mechanism-based inhibitors to this enzyme that may have therapeutic value (at this time the mammalian enzyme is thought to have a similar catalytic mechanism). / Thesis / Master of Science (MS)

The factors which regulate enzyme activity in the growing cell have been the subject of active research during the past decade and are generally considered under the heading of "metabolic control". At least three control parameters must be considered as regulating the active level of a given enzyme: control of enzyme synthesis at the gene level, control of enzyme activity by small molecule metabolites once the enzyme has been synthesized, and control of enzyme activity imposed by its structural orientation within the cell and/or its organelles (which would affect permeability of substrates, cofactors, etc.). It can be hypothesized that periodism in the intracellular level of a given metabolite must be accompanied by periodism in the active level of one or more of the enzymes responsible for the synthesis or breakdown of this metabolite. Synchronized cultures of microorganisms afford a unique tool for studying periodic changes in the intracellular levels of metabolites during cell growth. The studies presented in this thesis were designed to elucidate the relationships between the activity of Aspartate Transcarbamylase and factors which affect and are affected by the activity of this enzyme in synchronized cultures of Chlorella pyrenoidosa. Aspartate Transcarbamylase, the first enzyme in pyrimidine biosynthesis, has been reported to be controlled by a phenomenon known as " product-inhibition". This enzyme was located in the soluble supernatant of a 100,000 x g preparation of sonicated C. pyrenoidosa ceils. The pH optimum (9.2), temperature optimum (approx. 37°), and stability characteristics of this enzyme from this organism are reported. Aspartate Transcarbamylase when measured during two consecutive synchronous growth cycles in C. pyrenoidosa under continuous illumination was found to increase at alternating exponential rates in each growth cycle. When the increase in Aspartate Transcarbamylase was expressed in its logarithmic form, a plot with linear segments was obtained, each segment having a different slope. The rate of increase of Aspartate Transcarbamylase activity during early daughter cell development changes (increases) at the 5th h. The 5th through 9th h of cell growth, where Aspartate Transcarbamylase activity is increasing at an accelerated rate, corresponds to the premitotic and nuclear division stages in the cell. Correlated with this period of increased Aspartate Transcarbamylase activity (5th through 9th h) there is an increase in the rate of accumulation of RNA and DNA concurrent with increase in the rate of accumulation of intermediates in the acid-soluble, Norit-A adsorbable-P pool (which contains the nucleotide-P fraction). At. approximately the 9th h of cell growth there is a decrease in the rate of increase of Aspartate Transcarbamylase activity. Evidence is presented indicating that the depression of activity during this period is at least partly due to the presence of Norit-A adsorbable compound(s) present in the cell (pyrimidine nucleotides, the principal inhibitors of this enzyme, would be Norit-A adsorbable). At the 8th h of cell growth ( 1h prior to the period of depressed Aspartate Transcarbamylase activity) the acid-soluble, Norit-A adsorbable-P pool reaches a maximum value (as % of total cellular-P). These data together with inhibition studies with a variety of nucleoside mono-, di-, and tri-phosphates suggest that pyrimidine nucleotides may be factors regulating Aspartate Transcarbamylase activity during cellular development. / Ph. D.

Yes / Incoherent neutron spectroscopy, in combination with dynamic light scattering, was used to investigate the effect of ligand binding on the center-of-mass self-diffusion and internal diffusive dynamics of Escherichia coli aspartate α-decarboxylase (ADC). The X-ray crystal structure of ADC in complex with the D-serine inhibitor was also determined, and molecular dynamics simulations were used to further probe the structural rearrangements that occur as a result of ligand binding. These experiments reveal that D-serine forms hydrogen bonds with some of the active site residues, that higher order oligomers of the ADC tetramer exist on ns–ms time-scales, and also show that ligand binding both affects the ADC internal diffusive dynamics and appears to further increase the size of the higher order oligomers. / TR acknowledges a PhD studentship jointly funded by the ILL and the Universität Hamburg (Federal Excellence Cluster Hamburg Centre for Ultrafast Imaging EXC 1074).

Ketamine and phencyclidine (PCP) are noncompetitive antagonists of the N-methyl-D-aspartate (NMDA) type of ligand-gated glutamate receptors. Both agents have high abuse liability, and may produce dependence. Tolerance to the reinforcing effects of drugs of abuse is widely regarded as a key component of the dependence process. Therefore, the present study was conducted to examine whether tolerance develops to the reinforcing effects of ketamine, and whether PCP and dizocilpine, a noncompetitive NMDA antagonist with negligible abuse liability, produce cross-tolerance to the reinforcing effects of ketamine. Further, identification of the neural mechanisms that underlie tolerance to the reinforcing effects of drugs may yield information regarding drug dependence.