Phosphate bonds hydrolysis

Plapp FW, Casida JE. 1958. Hydrolysis of the alkyl-phosphate bond in certain dialkyl aryl phosphorothioate insecticides by rats, cockroaches, and alkali. J Econ Entomol 51 800-803. 

RNA is as suitable (if not more so) than DNA as a cleavage target [37]. In contrast to DNA, RNA is substantially less prone to oxidative cleavage [38] as a consequence of the higher stability of the glycosidic bond in ribonucleotides compared to that in deoxyribonucleotides. On the basis of the properties described in the introductory sections RNA is by contrast, much less stable to hydrolytic cleavage. For this reason the hydrolysis of the phosphate bond in this system can be successfully catalyzed not only by metal ions but also by ammonium ions. 

The charging of the tRNA molecule with the aminoacyl moiety requires the hydrolysis of an ATP to an AMP, equivalent to the hydrolysis of two ATPs to two ADPs and phosphates. The entry of the aminoacyl-tRNA into the A site results in the hydrolysis of one GTP to GDP. Translocation of the newly formed pep-tidyl-tRNA in the A site into the P site by EF2 similarly results in hydrolysis of GTP to GDP and phosphate. Thus, the energy requirements for the formation of one peptide bond include the equivalent of the hydrolysis of two ATP molecules to ADP and of two GTP molecules to GDP, or the hydrolysis of four high-energy phosphate bonds. A eukaryotic ribosome can incorporate as many as six amino acids per second prokaryotic ribosomes incorporate as many as 18 per second. Thus, the process of peptide synthesis occurs with great speed and accuracy until a termination codon is reached. 

Phosphate condensation reactions play an essential role in metabolism. Recall from Section 14.6 that the conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) requires an input of free energy ADP -I-H3 PO4 ATP +H2O AG° — +30.6kJ As also described in that section, ATP serves as a major biochemical energy source, releasing energy in the reverse, hydrolysis, reaction. The ease of interchanging O—H and O—P bonds probably accounts for the fact that nature chose a phosphate condensation/hydrolysis reaction for energy storage and transport. 

Schulz, W. G. Nieman, R. A. Skibo, E. B. Evidence for DNA phosphate backbone alkylation and cleavage by pyrrolo[l,2-a] benzimidazoles, small molecules capable of causing sequence specific phosphodiester bond hydrolysis. Proc. Natl. Acad. Sci. USA 1995, 92, 11854-11858. 

Ivie 1980) and quantification of its urinary metabolites in various animal species (Bucci et al. 1992 Hart 1976 Ivie 1980 Snodgrass and Metker 1992 Weiss et al. 1994). Hydrolysis of one of the two phosphate ester bonds liberates isopropanol and converts diisopropyl methylphosphonate to IMPA. The locations of the enzymes capable of catalyzing diisopropyl methylphosphonate phosphate ester hydrolysis have not been identified. 

Plant. In plants, mevinphos is hydrolyzed to phosphoric acid dimethyl ester, phosphoric acid, and other less toxic compounds (Hartley and Kidd, 1987). In one day, the compound is almost completely degraded in plants (Cremlyn, 1991). Casida et al. (1956) proposed two degradative pathways of mevinphos in bean plants and cabbage. In the first degradative pathway, cleavage of the vinyl phosphate bond affords methylacetoacetate and acetoacetic acid, which may be precursors to the formation of the end products dimethyl phosphoric acid, methanol, acetone, and carbon dioxide. In the other degradative pathway, direct hydrolysis of the carboxylic ester would yield vinyl phosphates as intermediates. The half-life of mevinphos in bean plants was 0.5 d (Casida et ah, 1956). In alfalfa, the half-life was 17 h (Huddelston and Gyrisco, 1961). 

The half-life of Fe2(OH)2" at room temperature is a few seconds. An improved model for the kinetics of dissociation of this dinuclear cation recognizes significan articipation by Fe2(OH)3 + at higher pHs, thus clearing up earlier slight anomalies in this area. Phosphate ester hydrolysis at the di-iron center of uteroferrin has now been shown to involve nucleophilic attack by bridging hydroxide (as proposed but not conclusively demonstrated for several M—OH—M-containing catalytic species) rather than by hydroxide bonded to just one Fe. ... 

Extraction is commonly carried out by hydrolysis in boiling acid such as chloridric acid or sulfuric acid. To release thiamine bonded to phosphate enzyme, hydrolysis with phosphatase, alone or together with claradiastase or takadiastase, is carried out. After the enzymatic digestion, an acid treatment is applied in order to precipitate the protein and denaturate the enzymes. Ndaw et al. [603] proved that for extraction of vitamins Bj, B, and Bg, acid hydrolysis is always superfluous if the activity of the enzymes chosen is sufficiently high. SPE or column chromatography may be used in further purification, mainly to remove excess of derivatization reagents used to convert thiamine to a highly flnorescent thiochrome derivatives. lEC may be used in purification step, as well. 

Proteins are costly to the cell, requiring hydrolysis of five high-energy phosphate bonds per amino acid incorporated. 

Fig. 3 Mechanisms for enzymatic supramolecular polymerisation (a) Formation of supramolecular assembly via bond cleavage, (b) Formation of supramolecular assemblies via bond formation. Examples are shown of biocatalytic supramolecular polymerisation of aromatic peptide amphiphiles via (i) phosphate ester hydrolysis, (ri) alkyl ester hydrolysis, and (iii) amide condensation or reversed hydrolysis using protease...

It is generally assumed that hydrolysis of the y-phosphate bond proceeds via an Sn2 mechanism, as shown in Fig. 5.17. The hydrolysis proceeds by an in-line attack of a water molecule on the y-phosphate, in which the GDP residue is displaced from the y-phosphate. 

In DNA and the related single-stranded RNA (ribonucleic acid), the phosphate units are monomeric and play a strictly structural role. Phosphates, however, are also essential to the metabolism of living cells, in which formation and subsequent hydrolysis of phosphate-phosphate bonds... 

Surface-catalyzed dark and photoassisted phosphate ester hydrolysis (P—O bond rupture) in aqueous suspensions of TiO2 has been proposed [6,7,41]. A number of products indicative of radical cationic pathways have been reported in the TiO2 photocatalysis of benzyl phosphonic acid [44]. 

Synthesis of SAM Methionine condenses with ATP, forming SAM—a high-energy compound that is unusual in that it cohlahs no phosphate. The formation of SAM is driven, in effect, by hydrolysis of all three phosphate bonds in ATP (see Figure 20.8). 

Sources of carbons, reducing equivalents, and energy sources As with fatty acids, all the carbon atoms in cholesterol are provided by acetate, and NADPH provides the reducing equivalents. The pathway is driven by hydrolysis of the high-energy thioester bond of acetyl CoA and the terminal phosphate bond of ATP. 

The high, negative AC0 values indicate that hydrolysis of the phosphate bond is strongly favoured thermodynamically. 

The pyrophosphate from the pyruvate-P dikinase is rapidly degraded so that, overall, the net price the plant pays for operation of this C02 pump is the hydrolysis of two high-energy phosphate bonds for every molecule of C02 transported ... 

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