Phosphoanhydride bonds hydrolysis

Hydrolysis of the terminal (or, /3-y) phosphoanhydride bond of ATP is the primary thermodynamic driving force in metabolism. Written as a biochemical equation at a specified pH, ATP hydrolysis can be represented as ... 

Inorganic pyrophosphatase [EC 3.6.1.1] plays a central role in phosphorus metabolism by catalyzing the hydrolysis of the phosphoanhydride bond of inorganic pyrophosphate (or, diphosphate PPi). This cleavage reaction acts in conjunction with pyrophosphate-forming ligases to provide an additional thermodynamic impetus for certain biosynthetic reactions. For example ... 

RGURE 8-40 The phosphate ester and phosphoanhydride bonds of ATP. Hydrolysis of an anhydride bond yields more energy than hydrolysis of the ester. A carboxylic acid anhydride and carboxylic acid ester are shown for comparison. 

Although the hydrolysis of ATP is highly exeigonic (AG ° = -30.5 kJ/mol), the molecule is kinetically stable at pH 7 because the activation energy for ATP hydrolysis is relatively high. Rapid cleavage of the phosphoanhydride bonds occurs only when catalyzed by an enzyme. 

FIGURE 13-11 Nucleoside triphosphates in RNA synthesis With each nucleoside monophosphate added to the growing chain, one PPi is released and hydrolyzed to two P,. The hydrolysis of two phosphoanhydride bonds for each nucleotide added provides the energy for forming the bonds in the RNA polymer and for assembling a specific sequence of nucleotides... 

Conversion of Succinyl-CoA to Succinate Succinyl-CoA, like acetyl-CoA, has a thioester bond with a strongly negative standard free energy of hydrolysis (AG ° = -36 kJ/mol). In the next step of the citric acid cycle, energy released in the breakage of this bond is used to drive the synthesis of a phosphoanhydride bond in either GTP or ATP, with a net AG ° of only -2.9 kJ/mol. Succinate is formed in the process ... 

The released energy of almost all the metabolic pathways is converted to the chemical energy of phosphoanhydride bonds in ATP. Cells use the energy released during hydrolysis of the ATP bonds to power energetically unfavorable processes. 

Structural formula of adenosine triphosphate (ATP) at pH 7.0, The three phosphate groups are identified by Greek letters a, fi, and y. The y- and S-phosphate groups are linked through phosphoanhydride bonds and their hydrolysis yields a large negative AG°, whereas the cr-phosphate linked by a phosphate ester bond has a much lower negative AG°. ... 

ATP is ideally suited to its role as universal energy currency because of its structure. ATP is a nucleotide composed of adenine, ribose, and a triphosphate unit (Figure 4.8). The two terminal phosphoryl groups (—PO32 ) are linked by phosphoanhydride bonds. Although anhydrides are easily hydrolyzed, the phos-phoanhydride bonds of ATP are sufficiently stable under mild intracellular conditions. Specific enzymes facilitate ATP hydrolysis. 

An ATP molecule has two key phosphoanhydride bonds (Figure 2-24). Hydrolysis of a phosphoanhydride bond ( ) In each of the following reactions has a highly negative AG of about —7.3 kcal/mol ... 

Many otherwise energetically unfavorable cellular processes are driven by hydrolysis of phosphoanhydride bonds In ATP (see Figure 2-24). 

Reaction (30) is favored as written for the formation of phosphoenolpyruvate by utilization of the energy of two phosphoanhydride bonds to phosphorylate pyruvate. Reaction (31) is energetically unfavored as written and would lead to the decomposition of phosphoenolpyruvate. This may be its function in some cells or under certain conditions (95). However, in the presence of inorganic pyrophosphatase to catalyze the hydrolysis of pyrophosphate, reaction (31) can also produce phosphoenolpyruvate. 

The hydrolysis of the phosphoanhydride bond of ATP releases inorganic phosphate and energy. In this coupled reaction catalyzed by an enzyme, the phosphoryl group and some of the released energy are transferred to (i-D-glucose. 

Here we see the final substrate-level phosphorylation in the pathway, which is catalyzed by pyruvate kinase. Phosphoenolpyruvate serves as a donor of the phospho-ryl group that is transferred to ADP to produce ATP This is another coupled reaction in which hydrolysis of the phosphoester bond in phosphoenolpyruvate provides energy for the formation of the phosphoanhydride bond of ATP. The final product of glycolysis is p)mivate. 

Adenosine triphosphate, ATP, is a nucleotide composed of adenine, the sugar ribose, and a triphosphate group. The energy released by the hydrolysis of the phosphoanhydride bond between the second and third phosphoryl groups provides the energy for most cellular work. 

Write a reaction showing the hydrolysis of the terminal phosphoanhydride bond of ATP. 

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