Hydrolysis of acetyl phosphate

For the hydrolysis of acetyl phosphate under the conditions prevailing in the body, AG = —41 kj-mol. If the phosphorylation of acetic acid (the reverse of the hydrolysis of acetyl phosphate) was driven by coupling to the hydrolysis of ATP at pH = 7, what is the minimum amount of ATP molecules (in moles) that would have to be hydrolyzed to form... 

Metal ions have a profound influence on the hydrolysis of acetyl phosphate, Thus, in the magnesium(ii)-catalysed system P—O bond flssion... 

Figure 1. Acid- and base-catalyzed hydrolysis of acetyl-phosphate. From G. Di Sabato Jencks (1961) J. Am. Chem. Soc. 83, 4400 reproduced with permission of the authors and the American Chemical Society.

CaOH1 and MgOH+ on free acyl phosphate is a likely reaction pathway for Ca11 and Mg11 catalysis of the base hydrolysis of acetyl phosphate. 

Gutsche et al. observed that a lipophilic dioxime (the ligand in 4) accelerates by a factor of 60 to 140 the hydrolysis of acetyl phosphate in the presence of an equimolar amount of metal (M = Cu, Zn, Ni) under comicellar conditions with cetyl trimethylammonium bromide (CTAB) at pH 11.5 [22], The hydrolysis reaction was followed by pseudo-first-order kinetics at [ligand] = [M] = 2.5 mM and [CTAB] = 250 mM. Although a possible complex 4 was proposed to exist in the hydroxamate form, there were no experimental data for the stability and structure of metal complexes at pH 11.5 (e.g., it is not known whether the... 

Micelles have been prepared from surfactants which contain a complexed metal ion, which can catalyze hydrolysis of organic phosphates and therefore can be regarded as akin to functional micelles [109]. These micelles are effective catalysts for the hydrolysis of acetyl phosphate and one can draw an analogy between them and metal-dependent enzymes involved in phosphoryl transfer. 

The hydrolysis of acetyl phosphate involves entropies and volumes of activation with values near zero. These and other kinetic properties are consistent with an S l mechanism involving the generation of free metaphosphate as an intermediate (Di Sabato and Jencks, 1961). Herschlag and Jencks (1986) have now shown that the data cited in support of the 8, 1... 

In addition to a multiple-turnover mechanism, inversion of stereochemistry may also result from the intermediacy of a phosphorylated enzyme carboxyl group (Scheme 3a).Breakdown via C—O bond cleavage results in overall stereochemical inversion. Hydrolysis of acetyl phosphate, catalysed by divalent metal ions, proceeds by predominant C—O cleavage (7.4 < pH < 8.2) (Klinman and Samuel, 1971). 

The volume of activation of the solvolysis of negative ions may also be indicative of mechanism. For example, the volumes of activation for the spontaneous hydrolysis of acetyl phosphate mono-anion and di-anioii in water at 39°C are —0 0 1 and —1 0 < 1 cm mole (Di Sabato et al., 1962). Consider, for example, a mechanism in which there is bimolecular attack of water on the anions. Since the P—0 bond breaks (Bentley, 1949 Park and Koshland, 1958),... 

The hydrolysis of acetyl phosphate has AG=-42 kJ mol" under typical biological conditions. If the phosphorylation of acetic acid were to be coupled to the hydrolysis of ATP. what is the minimum number of ATP molecules that would need to be involved ... 

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