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Modification of thiamine pyrophosphate dependent enzyme activity by oxythiamine in Saccharomyces cerevisiae cells

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Oxythiamine is an antivitamin derivative of thiamine that after phosphorylation to oxythiamine pyro phos phate can bind to the active centres of thiamine-dependent enzymes. In the present study, the effect of oxythiamine on the viability of Saccharomyces cerevisiae and the activity of thiamine pyrophosphate dependent enzymes in yeast cells has been investigated. We observed a decrease in pyruvate decarboxylase specific activity on both a control and an oxythiamine medium after the first 6 h of culture. The cytosolic enzymes transketolase and pyruvate decarboxylase decreased their specific activity in the presence of oxythiamine but only during the beginning of the cultivation. However, after 12 h of cultivation, oxythiamine-treated cells showed higher specific activity of cytosolic enzymes. More over, it was established by SDS–PAGE that the high specific activity of pyruvate decarboxylase was followed by an increase in the amount of the enzyme protein. In contrast, the mitochondrial enzymes, pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes, were inhibited by oxythiamine during the entire experiment. Our results suggest that the observed strong decrease in growth rate and viability of yeast on medium with oxythiamine may be due to stronger in hibition of mitochondrial pyruvate dehydrogenase than of cytosolic enzymes.Key words: pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase, transketolase, pyruvate decarboxylase, activity, oxythiamine, inhibition.

L'oxythiamine est une antivitamine dérivée de la thiamine qui suite à sa phosphorylation en oxythiamine pyrophosphate peut se lier aux centres d'enzymes dépendantes de la thiamine. Dans l'étude présente, nous avons examiné l'impact de l'oxythiamine sur la viabilité des Saccharomyces cerevisiae et sur l'activité d'enzymes dépendantes du TPP chez ces levures. Nous avons observé une diminution de l'activité spécifique de la PDC autant avec un milieu témoin et qu'avec un milieu contenant de l'oxythiamine après les premières 6 h de culture. Les enzymes cytosoliques transcétolase et pyruvate décarboxylase ont vu leur activité spécifique diminuée en présence d'oxythiamine mais seulement lors du début de la culture. Toutefois, après 12 h de culture, les cellules traitées à l'oxythiamine ont démontré une activité spécifique supérieure pour les enzymes cytosoliques. De plus, il fut estimé par SDS–PAGE que l'activité spécifique élevée de la PDC était suivie par une augmentation de l'expression de l'enzyme. En revanche, les enzymes mitochondriales, les complexes pyruvate déshydrogénase et 2-oxoglutarate déshydrogénase, furent inhibées par l'oxy thiamine tout au cours de l'expérience. Nos résultats indiquent que la diminution prononcée de la prolifération et de la viabilité des levures dans un milieu avec oxythiamine serait causée par une inhibition plus importante de la PDH mitochondriales que des enzymes cytosoliques.Mots clés : pyruvate déshydrogénase, 2-oxoglutarate déshydrogénase, transcétolase, pyruvate décarboxylase, activité, oxythiamine, inhibition.[Traduit par la Rédaction]

Document Type: Research Article

Publication date: 2005-09-01

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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