The Crenarchaea Sulfolobus solfataricus and S. acidocaldarius are among the best investigated Archaea and are well established as thermoacidophilic model organisms. The central carbohydrate metabolism (CCM) of Sulfolobus species has been well studied using classical biochemical and modern high throughput approaches such as genomics, proteomics and transcriptomics. However, the regulation of the CCM is still far from being understood. Like other archaea, Sulfolobus species lack the “classical” control points known from their eukaryotic or bacterial brethren and the only well established control point is the non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase, which is activated at low levels of the metabolite glucose 1-phosphate. Furthermore, the complexity of the CCM in Sulfolobus species as well as other Archaea is still unsolved and there are often several paralogs in the archaeal genomes with unknown function. In the first part of this thesis the impact of regulation by post translational modifications via reversible protein phosphorylation was analyzed in S. solfataricus and S. acidocaldarius. Crenarchaea like Sulfolobus species lack bacterial type one/two-component systems (phosphorylation on His and Asp) but rely on eukaryal like protein phosphorylation on Ser, Thr and Tyr. In S. solfataricus we investigated how the offered carbon source glucose (glycolytic growth) or tryptone (gluconeogenic growth) alter the global phosphorylation pattern. Analysis by precursor aquisition independent from ion count (PAcIFIC) revealed a high number of p-proteins (540) with a so far unique enrichment for p-Tyr (>50%) compared to previous studies in all three domains of life (Table 1). Furthermore, p-proteins were detected in all functional categories indicating a major impact on all cellular processes. In response to the carbon source dramatic changes in the phosphorylation pattern were observed. In the CCM especially proteins at the beginning of various sugar degradation pathways and gluconeogenic EMP and TCA and at branching points to other metabolic routs were targeted by protein phosphorylation. In S. acidocaldarius we used a similar experimental approach which combined transcriptomics, biochemistry and growth studies to investigate the effect of deletion of the two protein phosphatases. The respective genes of the putative protein phosphatases were cloned and the recombinant enzymes in regard to their substrate specificity investigated. The catalytic subunit of the protein Ser/Thr phosphatase (PP2Ac) resembles their eukaryotic counterparts and was inhibited by okadaic acid and requires Mn2+-ions for catalytic activity and showed strict activity towards p-Ser/p-Thr peptides. Whereas the protein tyrosine phosphatase (PTP) revealed dual substrate specificity with p-Tyr and p-Thr peptides. The phenotypic characterization of the three strains (MW001, Δsaci_pp2a, Δsaci_ptp) revealed that the parant strain MW001 and Δsaci_ptp resembled each other, where as the Δsaci_pp2a strain showed a differences in growth and cell size variation. The number of p-proteins in the background strain MW001 was lower (69) compared to S. solfataricus, but similar to that reported for other prokaryotic and eukaryotic organisms (Table 1). According to the expectation the number of p-proteins was increased in the two phosphatase deletion strains (Δsaci_pp2a (143), Δsaci_ptp (407)) and comparable to the number determined in S. solfataricus. However, the deletion of the two protein phosphatases not only resulted in an increase of p-proteins, the whole phosphorylation pattern was significant changed. The combination of the three data sets revealed that similar to S. solfataricus all cellular processes are targeted by protein phosphorylation. Furthermore, the investigation of the transcriptome, via RNA deep sequencing analysis, revealed a major impact on the transcription of genes of the respiratory chain as well as genes involved in cell motility (e.g. archaellum). These results were further supported by the identification of respective p-proteins and by the finding that the Δsaci_pp2a strain showed a different motility behavior compared to the strains MW001 and Δsaci_ptp. The CCM showed also a complete different phosphorylation pattern in MW001 compared to the two deletion strains. Especially enzymes of the tricarboxylic acid cycle as well as enzymes located at branching points (e.g. amino acid metabolism) seem to be targeted by protein phosphorylation in the Δsaci_pp2a strain. The high amount of p-Tyr detected in both Sulfolobus species let suggest that phosphorylation on Tyr is a crenarchaeal feature. The high growth temperature seems not to be the main reason of the high p-Tyr amount since only a low amount of p-Tyr was identified in the thermophilic gram-negative bacterium Thermus thermophilus (grown at 70°C, 10% p-Tyr). Also in the Euryarchaeota Halobacterium salinarium only one phosphorylation site on Tyr was identified, which excluds that this is a typical archaeal feature. However, compared to Sulfolobus species, T. thermophilus and H. salinarium also possess His kinases, which might provide alternative possibilities to regulate cellular functions by reversible protein phosphorylation. Therefore, suggesting that the high amount of p-Tyr is a typical feature of the crenarchaeal Sulfolobus species. The second part of this thesis focused on unraveling the complexity and regulation of the CCM in Sulfolobus species. From S. solfataricus were the triose-3-phosphate isomerase (TPI) and members of the aldehyde dehydrogenase super family characterized and from S. acidocaldarius the putative glucose-1-dehydrogenase (GDH). To unravel the function of the S. solfataricus TPI in gluconeogenesis kinetic parameters for both triose-3-phosphates glyceraldehydes-3-phosphate and dihydroxyacetone-3-phosphate were determined. The determined catalytic efficiencies were rather small compared to previously characterized archaeal TPIs. The reason is still unclear and we expect further insight from the available crystal structure. The S. solfataricus TPI showed inhibition by phosphoenolpyruvate and 3-phosphoglycerate which was not reported for any archaeal TPI so far but is well established for eukaryotic TPIs. For the two so far uncharacterized members of the aldehyde dehydrogenase super family succinic semialdehyde dehydrogenase activity was demonstrated (SSO1629, SSO1842) and a major role in polyamine and γ-aminobutyric acid metabolism was proposed based on bioinformatic analysis. For SSO1218 methylmalonate semialdehyde dehydrogenase activity demonstrated and a role in the degradation of branched amino acids was proposed. The characterization of the GDH from S. acidocaldarius (Saci_1079), one of the 12 of the medium-chain alcohol/polyol dehydrogenase/reductase branch of the pyridine nucleotide-dependent alcohol/polyol/sugar dehydrogenase superfamily in S. acidocaldarius, revealed that this enzyme exhibits broad substrate specificity a broad range of different sugars and might play an important role not only in D-glucose, but also in D-xylose, D-galactose and D-fucose degradation. The enzyme shows highest similarity to GDH-1 (SSO3003) of S. solfataricus and resembles the enzyme in respect to its broad substrate specificity, kinetic parameters as well as structural features. Notably, some of the enzymes (e.g. SSO1842, Saci_1079) have been identified as p-proteins and future studies aim to unravel the impact of phosphorylation on enzyme function in order to resolve the respective signal transduction pathways.