Pyruvate kinases from Archaea
Pyruvate kinases (PK) catalyze the final step of glycolysis in all three domains of life. Most PKs display sigmoidal kinetics with respect to PEP and/or ADP indicating cooperative binding of substrate. In addition, PKs from bacteria and eukarya are allosterically activated by sugar phosphates, e.g. fructose 1,6-bisphosphate (FBP), or by AMP as shown for PK of the hyperthermophilic bacterium Thermotoga maritima. In our studies we found that PKs from hyperthermophilic archaea are not activated by any of the classical allosteric effectors. The structure of PK from the hyperthermophilic archaeon Pyrobaculum aerophilum was solved, explaining why FBP cannot act as an allosteric activator of PK activity. Instead, we identified 3-phosphoglycerate (3PG) as a novel type of allosteric activator.
Allosteric activation of PK from Pyrobaculum by 3-phosphoglycerate (3PG).
Allosteric domain of PK structure of Pyrobaculum with bound 3PG
In bacteria and eukarya glucose is degraded via classical glycolysis (Embden-Meyerhof EM pathway) to pyruvate. This classical pathway is coordinated regulated inter alia by the product of the irreversible enzyme phosphofructokinase FBP. In contrast, in the archaeon P. aerophilum glucose is degraded via a modified version of the EM pathway in particular GAP oxidation to 3PG is catalyzed by the irreversible one-step reaction of glycerinaldehyde-3-phosphate oxidoreductase (GAPOR), whereas in bacteria and eukarya GAP is oxidized by a reversible two-step reaction catalyzed by GAPDH and GK. Regulation of P. aerophilum PK by a carboxylate molecule (3PG) rather than a sugar phosphate (FBP) may reflect a step in the evolution of glycolysis that predates the dominance of sugars in metabolism.
Classical Embden-Meyerhof pathway and its modification in the hyperthermophilic archaeon P. aerophilum. This schematic shows (A) the modified EM pathway of P. aerophilum and (B) the classical EM pathway of eukarya and bacteria. Irreversible enzymes that operate in each pathway are designated by red arrows, and intermediates that activate PK are shown in red boxes
Solomons et al. (2013) 3-Phosphoglycerate is an allosteric activator of pyruvate kinase from the hyperthermophilic archaeon Pyrobaculum aerophilum. Biochemistry 52: 5865-75
Johnsen et al. (2003) Comparative analysis of pyruvate kinases from the hyperthermophilic archaea Archaeoglobus fulgidus, Aeropyrum pernix, and Pyrobaculum aerophilum and the hyperthermophilic bacterium Thermotoga maritima: Unusual regulatory properties in hpyerthermophilic archaea. J Biol Chem 278: 25417-27