Acetyl phosphate free energy

The standard-state free energy of hydrolysis for acetyl phosphate is AG° = —42.3 kj/mol. 

Calculate the free energy change for acetyl phosphate hydrolysis in a solution of 2 mM acetate, 2 mM phosphate, and 3 iiM acetyl phosphate. 

A coupled process links a spontaneous reaction with a nonspontaneous one. In this case, the negative free energy change of the acetyl phosphate reaction drives the conversion of ADP to ATP. 

The negative value of A Gjjg shows that the free energy released in the acetyl phosphate reaction is more than enough to drive the conversion of ADP to ATP. 

The highly electrophilic character of the POf ion would suggest a very unselective phosphorylation behavior. For example, the ratio of alkyl phosphate to inorganic phosphate obtained in hydrolyses of phosphoric esters in water/alcohol mixtures should reflect the molar ratio of water and alcohol. This is indeed found in numerous cases, e.g. in the hydrolysis of phenyl and 4-nitrophenyl phosphate monoanions 97) or of 4-nitrophenyl phosphate dianions 65) at 100 °C in methanol/ water mixtures of various compositions, as also in the solvolysis of the acetyl phosphate dianion at 37 °C 97) or of phosphoenol pyruvate monoanions 82). Calculations of the free energy of the addition reactions of water and ethanol to the POf ion support the energetic similarity of the two reactions 98) (Table 4). 

AcK acetate kinase AcP acetyl phosphate AdK adenylate kinase AP A p ,pn-di(adenosine 5 -) n-phosphate ARS aminoacyl tRNA synthetase ATP, ADP, AMP adenosine 5 -tri-, di-, monophosphate ATP-u-S (Sp)-adenosine 5 -0-(l-thiotriphos-phate), ATP-y-S adenosine 5 -0-(3-thiotriphosphate) CK carbamyl kinase CP carbamyl phosphate CrK creatine kinase CTP, CDP, CMP cytidine 5 -tri-, di-, monophosphate dATP, dAMP deoxyadenosine 5 -tri-, monophosphate DNA deoxyribonucleic acid AG change in free energy GK glycerol kinase GTP, GDP, GMP guanosine 5 -tri-, di-, monophosphate HK hexokinase IUB International Union of Biochemistry MCP methoxycarbonyl phosphate NTP, NDP, NMP nucleoside 5 -tri-, di-, monophosphate PC phosphocreatine PEP phosphoenol pyruvate P orthophosphate PK pyruvate kinase P polyphosphate PnK poly-... 

The structurally similar amino acid-RNA derivatives also react rapidly with hydroxylamine and are energy-rich compounds, since they are in reversible equilibrium with ATP (Hoagland et al, 1958 Mager and Lipmann, 1958 Holley and Goldstein, 1959). Within the acyl phosphate series, acetyl adenylate (1737 cm ) has a free energy of hydrolysis at pH 7 which is similar to that of acetylimidazole and is... 

It should be noted that isoprenoid biosynthesis requires acetyl-CoA, ATP, and NADPH. The physiological source of these compounds is presumably sugar phosphate metabolism, via glycolysis and the pentose phosphate pathway. We show sucrose as the starting material in Fig. 1, since it is the principal transport sugar in plants. Free acetate is not an important metabolite in plants acetyl-CoA is normally derived from pyruvate formed in glycolysis. Biosynthesis of terpenes implies that acetyl-CoA is diverted from the Krebs cycle and that the energy available from the Krebs cycle and oxidative phos-... 

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