@article {432,
	title = {Metabolic response of Geobacter sulfurreducens towards electron donor/acceptor variation.},
	journal = {Microb Cell Fact},
	volume = {9},
	year = {2010},
	month = {2010},
	pages = {90},
	abstract = {BACKGROUND: Geobacter sulfurreducens is capable of coupling the complete oxidation of organic compounds to iron reduction. The metabolic response of G. sulfurreducens towards variations in electron donors (acetate, hydrogen) and acceptors (Fe(III), fumarate) was investigated via (13)C-based metabolic flux analysis. We examined the (13)C-labeling patterns of proteinogenic amino acids obtained from G. sulfurreducens cultured with (13)C-acetate.

RESULTS: Using (13)C-based metabolic flux analysis, we observed that donor and acceptor variations gave rise to differences in gluconeogenetic initiation, tricarboxylic acid cycle activity, and amino acid biosynthesis pathways. Culturing G. sulfurreducens cells with Fe(III) as the electron acceptor and acetate as the electron donor resulted in pyruvate as the primary carbon source for gluconeogenesis. When fumarate was provided as the electron acceptor and acetate as the electron donor, the flux analysis suggested that fumarate served as both an electron acceptor and, in conjunction with acetate, a carbon source. Growth on fumarate and acetate resulted in the initiation of gluconeogenesis by phosphoenolpyruvate carboxykinase and a slightly elevated flux through the oxidative tricarboxylic acid cycle as compared to growth with Fe(III) as the electron acceptor. In addition, the direction of net flux between acetyl-CoA and pyruvate was reversed during growth on fumarate relative to Fe(III), while growth in the presence of Fe(III) and acetate which provided hydrogen as an electron donor, resulted in decreased flux through the tricarboxylic acid cycle.

CONCLUSIONS: We gained detailed insight into the metabolism of G. sulfurreducens cells under various electron donor/acceptor conditions using (13)C-based metabolic flux analysis. Our results can be used for the development of G. sulfurreducens as a chassis for a variety of applications including bioremediation and renewable biofuel production.},
	keywords = {Acetic Acid, Acetyl Coenzyme A, Amino Acids, Carbon Isotopes, Citric Acid Cycle, Electrons, Ferric Compounds, Fumarates, Geobacter, Gluconeogenesis, Oxidation-Reduction, Phosphoenolpyruvate Carboxykinase (GTP), Pyruvates},
	issn = {1475-2859},
	doi = {10.1186/1475-2859-9-90},
	author = {Yang, Tae Hoon and Coppi, Maddalena V and Lovley, Derek R and Sun, Jun}
}
@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 = {<p>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.</p>},
	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}
}
