@article {1219, title = {Key role for sulfur in peptide metabolism and in regulation of three hydrogenases in the hyperthermophilic archaeon Pyrococcus furiosus.}, journal = {J Bacteriol}, volume = {183}, year = {2001}, month = {2001 Jan}, pages = {716-24}, abstract = {

The hyperthermophilic archaeon Pyrococcus furiosus grows optimally at 100 degrees C by the fermentation of peptides and carbohydrates. Growth of the organism was examined in media containing either maltose, peptides (hydrolyzed casein), or both as the carbon source(s), each with and without elemental sulfur (S(0)). Growth rates were highest on media containing peptides and S(0), with or without maltose. Growth did not occur on the peptide medium without S(0). S(0) had no effect on growth rates in the maltose medium in the absence of peptides. Phenylacetate production rates (from phenylalanine fermentation) from cells grown in the peptide medium containing S(0) with or without maltose were the same, suggesting that S(0) is required for peptide utilization. The activities of 14 of 21 enzymes involved in or related to the fermentation pathways of P. furiosus were shown to be regulated under the five different growth conditions studied. The presence of S(0) in the growth media resulted in decreases in specific activities of two cytoplasmic hydrogenases (I and II) and of a membrane-bound hydrogenase, each by an order of magnitude. The primary S(0)-reducing enzyme in this organism and the mechanism of the S(0) dependence of peptide metabolism are not known. This study provides the first evidence for a highly regulated fermentation-based metabolism in P. furiosus and a significant regulatory role for elemental sulfur or its metabolites.

}, keywords = {Culture Media, Cytoplasm, Gene Expression Regulation, Archaeal, Gene Expression Regulation, Enzymologic, Glycolysis, Hydrogenase, Membrane Proteins, Oxidation-Reduction, Peptides, Pyrococcus furiosus, Sulfur}, issn = {0021-9193}, doi = {10.1128/JB.183.2.716-724.2001}, author = {Adams, M W and Holden, J F and Menon, A L and Schut, G J and Grunden, A M and Hou, C and Hutchins, A M and Jenney, F E and Kim, C and Ma, K and Pan, G and Roy, R and Sapra, R and Story, S V and Verhagen, M F} } @article {1199, title = {Phosphoenolpyruvate synthetase from the hyperthermophilic archaeon Pyrococcus furiosus.}, journal = {J Bacteriol}, volume = {183}, year = {2001}, month = {2001 Jan}, pages = {709-15}, abstract = {

Phosphoenolpyruvate synthetase (PpsA) was purified from the hyperthermophilic archaeon Pyrococcus furiosus. This enzyme catalyzes the conversion of pyruvate and ATP to phosphoenolpyruvate (PEP), AMP, and phosphate and is thought to function in gluconeogenesis. PpsA has a subunit molecular mass of 92 kDa and contains one calcium and one phosphorus atom per subunit. The active form has a molecular mass of 690+/-20 kDa and is assumed to be octomeric, while approximately 30\% of the protein is purified as a large ( approximately 1.6 MDa) complex that is not active. The apparent K(m) values and catalytic efficiencies for the substrates pyruvate and ATP (at 80 degrees C, pH 8.4) were 0.11 mM and 1.43 x 10(4) mM(-1). s(-1) and 0.39 mM and 3.40 x 10(3) mM(-1) x s(-1), respectively. Maximal activity was measured at pH 9.0 (at 80 degrees C) and at 90 degrees C (at pH 8.4). The enzyme also catalyzed the reverse reaction, but the catalytic efficiency with PEP was very low [k(cat)/K(m) = 32 (mM. s(-1)]. In contrast to several other nucleotide-dependent enzymes from P. furiosus, PpsA has an absolute specificity for ATP as the phosphate-donating substrate. This is the first PpsA from a nonmethanogenic archaeon to be biochemically characterized. Its kinetic properties are consistent with a role in gluconeogenesis, although its relatively high cellular concentration ( approximately 5\% of the cytoplasmic protein) suggests an additional function possibly related to energy spilling. It is not known whether interconversion between the smaller, active and larger, inactive forms of the enzyme has any functional role.

}, keywords = {Adenosine Monophosphate, Adenosine Triphosphate, Gluconeogenesis, Hydrogen-Ion Concentration, Phosphates, Phosphoenolpyruvate, Phosphotransferases (Paired Acceptors), Pyrococcus furiosus, Pyruvic Acid, Substrate Specificity}, issn = {0021-9193}, doi = {10.1128/JB.183.2.709-715.2001}, author = {Hutchins, A M and Holden, J F and Adams, M W} }