The central carbohydrate metabolism of the hyperthermophilic crenarchaeote Thermoproteus tenax: pathways and insights into their regulation.

Although the complexity and modifications of the archaeal central carbohydrate metabolism (CCM) are well established, the knowledge about its regulation is rather limited. The facultatively heterotrophic, hyperthermophilic crenarchaeote Thermoproteus tenax utilizes a modified version of the reversible Embden-Meyerhof-Parnas (EMP) and the catabolic, branched Entner-Doudoroff (ED) pathway for glucose metabolism. Glucose is completely oxidized to carbon dioxide via the oxidative tricarboxylic acid (TCA) cycle, which is supposedly used in the reductive direction for carbon dioxide fixation under autotrophic growth conditions. Elemental sulfur is used as final electron acceptor. The CCM of T. tenax has been well studied on protein level as well as on gene level by performing a focused transcriptional analysis (CCM DNA microarray). In contrast to the classical pathways found in Bacteria and Eucarya allosteric regulation seems to play a minor role, therefore emphasizing the important role of regulation on transcript level in T. tenax. Whereas the EMP pathway and the TCA cycle show a highly coordinated regulation on gene level, the catabolic, branched ED pathway reveals no strong regulation. The CCM pathways in T. tenax and the current understanding of their regulation are presented.