The branched Entner-Doudoroff pathway in Thermoproteus tenax: Enzymes, regulation and physiological function

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The general understanding of central carbohydrate metabolism in Archaea comprises the presence of the non-nonphosphorylative Entner-Doudoroff (ED) pathway in (hyper)thermophilic Archaea and of the semi-phosphoryltive ED pathway in halophilic Archaea. However, a recent combined comparative genomics and biochemical approach revealed the presence of the semi-phosphorylative pathway in the hyperthermophilic Crenarchaeota Thermoproteus tenax and Sulfolobus solfataricus. Initial biochemical studies led to the identification of i) a novel type of gluconate dehydratase ii) a bifunctional 2-keto-3-deoxy-(6-phospho-)gluconate (KD(P)G) aldolase, iii) the first archaeal 2-keto-3-deoxygluconate (KDG) kinase and iv) a glycerate kinase. These results suggest the presence of both ED modifications (semi- and non-phosphorylative) and thus a branched ED pathway in these organisms. In T. tenax the suggested branched ED pathway is active in addition to the well studied Embden-Meyerhof-Parnas (EMP) modification and seems to be specific for glucose, whereas it represents the only “promiscuous” route for glucose and galactose degradation in S. solfataricus. The goal of this proposed study is to confirm the presence of the branched ED pathway in T. tenax, study its enzymes, their stereoselectivity/promiscuity, as well as the regulation and physiological function of the pathway. To gain an integrated understanding, the proposed studies will be combined in different collaborations with structural biology, phylogenetic studies as well as modern high-throughput approaches (proteomics/phosphorylomics, transcriptomics). This project will not only contribute to the understanding of the archaeal central carbohydrate metabolism and its regulation, but will aid to further unravel the metabolic complexity in all three domains of life.