138-08-9Relevant articles and documents
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Clark,V.M.,Kirby,A.J.
, p. 3705 - 3706 (1963)
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Schmidt,Thannhauser
, p. 370 (1943)
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Sutherland,Posternak,Cori
, p. 157 (1949)
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Meyerhof,Kiessling
, (1935)
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Thermodynamics of the hydrolysis reactions of adenosine 3′,5′-(cyclic)phosphate(aq) and phosphoenolpyruvate(aq); the standard molar formation properties of 3′,5′-(cyclic)phosphate(aq) and phosphoenolpyruvate(aq)
Goldberg, Robert N.,Tewari, Yadu B.
, p. 1809 - 1830 (2007/10/03)
Molar calorimetric enthalpy changes ΔrHm(cal) have been measured for the biochemical reactions {cAMP(aq) + H2O(l) = AMP(aq)} and {PEP(aq) + H2O(l) = pyruvate(aq) + phosphate(aq)}. The reactions were catalyzed, respectively, by phosphodiesterase 3prime;,5prime;-cyclic nucleotide and by alkaline phosphatase. The results were analyzed by using a chemical equilibrium model to obtain values of standard molar enthalpies of reaction ΔrHmo for the respective reference reactions {cAMp-(aq) + H2O(l) = HAMP-(aq)} and {PEP3-(aq) + H2O(l) = pyruvate-(aq) + HPO42-(aq)}. Literature values of the apparent equilibrium constants K′ for the reactions {ATP(aq) = cAMP(aq) + pyrophosphate(aq)K {ATP(aq) + pyruvate(aq) = ADP(aq) + PEP(aq)}, and {ATP(aq) + pyruvate(aq) + phosphate(aq) = AMP(aq) + PEP(aq) + pyrophosphate(aq)} were also analyzed by using the chemical equilibrium model. These calculations yielded values of the equilibrium constants K and standard molar Gibbs free energy changes ΔrGmo for ionic reference reactions that correspond to the overall biochemical reactions. Combination of the standard molar reaction property values (K, ΔrH mo, and ΔrGmo) with the standard molar formation properties of the AMP, ADP, ATP, pyrophosphate, and pyruvate species led to values of the standard molar enthalpy ΔfHmo, and Gibbs free energy of formation ΔfGmo and the standard partial molar entropy Smo of the cAMP and PEP species. The thermochemical network appears to be reasonably well reinforced and thus lends some confidence to the accuracy of the calculated property values of the variety of species involved in the several reactions considered herein. Published by Elsevier Ltd.
Nonenzymatic breakdown of the tetrahedral (α-carboxyketal phosphate) intermediates of MurA and AroA, two carboxyvinyl transferases. Protonation of different functional groups controls the rate and fate of breakdown
Byczynski, Bartosz,Mizyed, Shehadeh,Berti, Paul J.
, p. 12541 - 12550 (2007/10/03)
The mechanisms of nonenzymatic breakdown of the tetrahedral intermediates (THIs) of the carboxyvinyl transferases MurA and AroA were examined in order to illuminate the interplay between the inherent reactivities of the THIs and the enzymatic strategies used to promote catalysis. THI degradation was through phosphate departure, with C-O bond cleavage. It was acid catalyzed and dependent on the protonation state of the carboxyl of the α-carboxyketal phosphate functionality, with ionizations at pKa = 3.2 ± 0.1 and 4.3 ± 0.1 for MurA and AroA THIs, respectively. The solvent deuterium kinetic isotope effect for MurA THI at pL 2.0 was 1.3 ± 0.4, consistent with general acid catalysis. The pKa's suggested intramolecular general acid catalysis through protonation of the bridging oxygen of the phosphate, though H3O+ catalysis was also possible. The product distribution varied with pH. The dominant breakdown products were {pyruvate + phosphate + R-OH} (R-OH = UDP-GlcNAc or shikimate 3-phosphate) at all pH's, particularly low pH. At higher pH's, increasing proportions of ketal, arising from intramolecular substitution of phosphate by the adjacent hydroxyl and the enolpyruvyl products of phosphate elimination were observed. With MurA THI, the product distribution fitted to pK a's 1.6 and 6.2, corresponding to the expected pKa's of a phosphate monoester. C-O bond cleavage was demonstrated by the lack of monomethyl [33P]phosphate formed upon degrading MurA [ 33P]THI in 50% methanol. General acid catalysis through the bridging oxygen is consistent with the location of the previously proposed general acid catalyst for THI breakdown in AroA, Lys22.
