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See detailUp-regulation of 2-oxoglutarate dehydrogenase as a stress response
Graf, Anastasia; Trofimova, Lidia; Loshinskaja, Alexandra et al

in International Journal of Biochemistry & Cell Biology (2013), 45

2-Oxoglutarate dehydrogenase multienzyme complex (OGDHC) operates at a metabolic cross-road, mediating Ca2+- and ADP-dependent signals in mitochondria. Here, we test our hypothesis that OGDHC plays a ... [more ▼]

2-Oxoglutarate dehydrogenase multienzyme complex (OGDHC) operates at a metabolic cross-road, mediating Ca2+- and ADP-dependent signals in mitochondria. Here, we test our hypothesis that OGDHC plays a major role in the neurotransmitter metabolism and associated stress response. This possibility was assessed using succinyl phosphonate (SP), a highly specific and efficient in vivo inhibitor of OGDHC. Animals exposed to toxicants (SP, ethanol or MnCl2), trauma or acute hypoxia showed intrinsic up-regulation of OGDHC in brain and heart. The known mechanism of the SP action as OGDHC inhibitor pointed to the up-regulation triggered by the enzyme impairment. The animal behavior and skeletal muscle or heart performance were tested to correlate physiology with the OGDHC regulation and associated changes in the glutamate and cellular energy status. The SP-treated animals exhibited interdependent changes in the brain OGDHC activity, glutamate level and cardiac autonomic balance, suggesting the neurotransmitter role of glutamate to be involved in the changed heart performance. Energy insufficiency after OGDHC inhibition was detectable neither in animals up to 25 mg/kg SP, nor in cell culture during 24 h incubation with 0.1 mM SP. However, in animals subjected to acute ethanol intoxication SP did evoke energy deficit, decreasing muscular strength and locomotion and increasing the narcotic sleep duration. This correlated with the SP-induced decrease in NAD(P)H levels of the ethanol-exposed neurons. Thus, we show the existence of natural mechanisms to up-regulate mammalian OGDHC in response to stress, with both the glutamate neurotransmission and energy production potentially involved in the OGDHC impact on physiological performance. [less ▲]

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See detailMitotic spindle: focus on the function of huntingtin
Godin, Juliette ULg; Humbert, Sandrine

in International Journal of Biochemistry & Cell Biology (2011), 43(6), 852-856

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See detailHuman recombinant thiamine triphosphatase: purification, secondary structure and catalytic properties
Lakaye, Bernard ULg; Makarchikov, Alexander F; Wins, Pierre et al

in International Journal of Biochemistry & Cell Biology (2004), 36(7), 1348-1364

Thiamine triphosphate (ThTP) is found in most living organisms and it may act as a phosphate donor for protein phosphorylation. We have recently cloned the cDNA coding for a highly specific mammalian 25 ... [more ▼]

Thiamine triphosphate (ThTP) is found in most living organisms and it may act as a phosphate donor for protein phosphorylation. We have recently cloned the cDNA coding for a highly specific mammalian 25 kDa thiamine triphosphatase (ThTPase; EC 3.6.1.28). As the enzyme has a high catalytic efficiency and no sequence homology with known phosphohydrolases, it was worth investigating its structure and catalytic properties. For this purpose, we expressed the untagged recombinant human ThTPase (hThTPase) in E. coli, produced the protein on a large scale and purified it to homogeneity. Its kinetic properties were similar to those of the genuine human enzyme, indicating that the recombinant hThTPase is completely functional. Mg2+ ions were required for activity and Ca2+ inhibited the enzyme by competition with Mg2+. With ATP as substrate, the catalytic efficiency was 10(-4)-fold lower than with ThTP, confirming the nearly absolute specificity of the 25 kDa ThTPase for ThTP. The activity was maximum at pH 8.5 and very low at pH 6.0. Zn2+ ions were inhibitory at micromolar concentrations at pH 8.0 but activated at pH 6.0. Kinetic analysis suggests an activator site for Mg2+ and a separate regulatory site for Zn2+. The effects of group-specific reagents such as Woodward's reagent K and diethylpyrocarbonate suggest that at least one carboxyl group in the active site is essential for catalysis, while a positively charged amino group may be involved in substrate binding. The secondary structure of the enzyme, as determined by Fourier-transform infrared spectroscopy, was predominantly beta-sheet and alpha-helix. [less ▲]

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See detailExpression of 25 kDa thiamine triphosphatase in rodent tissues using quantitative PCR and characterization of its mRNA
Lakaye, Bernard ULg; Verlaet, Myriam ULg; Dubail, Johanne ULg et al

in International Journal of Biochemistry & Cell Biology (2004), 36(10), 2032-2041

Thiamine triphosphate (ThTP) is found in most organisms, but its biological role remains unclear. In mammalian tissues, cellular ThTP concentrations remain low, probably because of hydrolysis by a ... [more ▼]

Thiamine triphosphate (ThTP) is found in most organisms, but its biological role remains unclear. In mammalian tissues, cellular ThTP concentrations remain low, probably because of hydrolysis by a specific 25 kDa thiamine triphosphatase (ThTPase). The aim of the present study was to use quantitative PCR, for comparing the 25 kDa ThTPase mRNA expression in various mouse tissues with its enzyme activities. ThTPase mRNA was expressed at only a few copies per cell. The highest amount of mRNA was found in testis, followed by lung and muscle, while the highest enzyme activities were found in liver and kidney. The poor correlation between mRNA levels and enzyme activities might result either from tissue-specific post-transcriptional regulation of mRNA processing and/or translation or from the regulation of enzyme activities by post-translational mechanisms. Purified recombinant human ThTPase was phosphorylated by casein kinase 11, but this phosphorylation did not modify the enzyme activity. However, the characterization of the 3'-untranslated mRNA region revealed a unique, highly conserved, 200-nucleotide sequence that might be involved in translational control. In situ hybridization studies in testis suggest a predominant localization of ThTPase mRNA in poorly differentiated spermatogenic cells. This is the first study demonstrating a cell-specific 25 kDa ThTPase mRNA expression, suggesting that this enzyme might be related to the degree of differentiation or the metabolic state of the cell. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailThe HOXC6 homeodomain-containing proteins
Chariot, Alain ULg; Gielen, jacques

in International Journal of Biochemistry & Cell Biology (1998), 30

The HOXC6 homeodomain-containing proteins act as transcription factors in the genetic control of multiple genes involved in development and cell differentiation. Two HOXC6 polypeptides are encoded by a ... [more ▼]

The HOXC6 homeodomain-containing proteins act as transcription factors in the genetic control of multiple genes involved in development and cell differentiation. Two HOXC6 polypeptides are encoded by a single homeobox ('HOX') gene described as 'master gene' for the crucial role it plays in the patterning and axial morphogenesis of multiple species. Transcription of the HOXC6 gene is initiated from two promoters and generates two proteins that share the same DNA-binding domain but harbor a distinct N-terminal region. Recent studies have demonstrated that both HOXC6 products can activate or repress transcription, depending on the cellular context. Functional in vivo specificity of HOXC6 proteins may be achieved through combinatorial interactions with other members of the HOX family as well as with co-factors whose identities are largely unknown. Disruption of this 'HOX code' may lead to pathology such as developmental defects. [less ▲]

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