Phosphate-ester bond

Phosphonates are organic phosphates characterized by a C-P-O bond, which is much more resistant to hydrolysis than the polyphosphate bond (O-P-O) or the phosphate ester bond (C-O-P), making them suitable for many types of BW treatment formulation. Phosphonates were originally developed for the industrial and institutional (I I) cleaning market in the 1960s, but are commonly employed in a myriad of applications. 

The contractile apparatus may be thought of as the sum of those intracellular components which constitute the machinery of chemomechanical transduction. It is the set of proteins which convert the chemical energy of the terminal phosphate ester bond of ATP into mechanical work. The structure of the contractile apparatus is determined by the connections between the various protein molecules via specific binding sites or, in a minority of cases, via labile covalent linkages. The kinetics of the contractile machinery are determined by the regulation of changes in these connections. 

Many of the most fundamental biochemicals required for life contain P generally linked to long, complicated organic molecules by phosphate ester bonds. Among the impressive list of... 

Phosphate also plays a central role in the transmission and control of chemical energy within the cells primarily via the hydrolysis of the terminal phosphate ester bond of the adenosine triphosphate (ATP) molecule (Fig. 14-3b). In addition, phosphate is a necessary constituent of phospholipids, which are important components in cell membranes, and as mentioned before, of apatite, which forms structural body parts such as teeth and bones. It is not surprising, therefore, that the cycling of P is closely linked with biological processes. This connection is, in fact, inseparable as organisms cannot exist without P, and their existence controls, to a large extent, the natural distribution of P. 

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. 

The focus of this account is on low molecular weight metal complexes that mimic the cooperation of two metal ions in the hydrolytic cleavage of phosphate ester bonds. 

Mono-, di- and triacylglycerols may all be measured by determination of the amount of glycerol released by hydrolysis. The lipid is first extracted into chloroform-methanol (2 1) and saponification is performed under conditions that will not affect any phosphate ester bonds, otherwise glycerol originating from phosphoglycerides would also be measured. Heating at 70°C for 30 min with alcoholic potassium hydroxide (0.5 mol l-1) has been shown to be satisfactory. However, the phospholipids may be removed prior to saponification either by extraction or by adsorption on activated silicic acid. 

The conversion of parathion is affected by soil constituents in the order kaolinite > smectite > organic matter and is related inversely to the adsorption affinity of these materials for this contaminant (Mingelgrin and Saltzman 1977). Although the extent of hydrolysis differs among soils, it is apparent that soil-surface degradation of parathion is caused by hydrolysis of the phosphate ester bond. The presence of water in the soil-parathion system led to a decrease in the surface-induced degradation of the organic molecule and diminished the effect of natural soil properties on its persistence. 

In addition to receptor t)rrosine kinases, which catalyse the formation of phosphate ester bond, protein phosphatases also play an important role in regulating signalling pathways. They... 

Phosphoenolpyruvate (Fig. 13-3) contains a phosphate ester bond that undergoes hydrolysis to yield the enol form of pyruvate, and this direct product can immediately tautomerize to the more stable keto form of pyruvate. Because the reactant (phosphoenolpyruvate) has only one form (enol) and the product (pyruvate) has two possible forms, the product is stabilized relative to the reactant. This is the greatest contributing factor to the high standard free energy of hydrolysis of phosphoenolpyruvate AG ° = -61.9 kJ/mol. 

FIGURE 16-3 Coenzyme A (CoA). A hydroxyl group of pantothenic acid is joined to a modified ADP moiety by a phosphate ester bond, and its carboxyl group is attached to /3-mercaptoethylamine in amide linkage. The hydroxyl group at the 3 position of the ADP moiety has a phosphoryl group not present in free ADP. The —SH group of the mercaptoethylamine moiety forms a thioester with acetate in acetyl-coenzyme A (acetyl-CoA) (lower left). 

Of particular importance is the conversion of much of the energy that results from photosynthesis, or from the oxidation of fats, carbohydrates, and proteins in cells into formation of phosphate ester bonds (C—O—P) or phosphate anhydride bonds (P—O—P). The energy so stored is used in other reactions, the net result of which is hydrolysis ... 

FADH2 (Section 15-6C). Polynucleotides are polymers of nucleosides linked through phosphate ester bonds. Polynucleotides also are called nucleic acids (RNA and DNA) and are the genetic material of cells, as will be discussed in Chapter 25. 

It would be attractive to speculate that as part of the enzymic reaction Tyr 113 donated a proton to the 5 -phosphate ester bond (59). Since the enzyme is active when Tyr 113 is nitrated (33) and thus almost certainly present as a phenolate ion at the optimum pH, this idea... 

Ribonuclease T2 is regarded as a nonspecific endoribonuclease [EC 2.7.7.17, ribonucleate nucleotido-2 -transferase (cyclizing)]. It preferentially splits the internucleotide bonds between the 3 -adenylic acid group and the 5 -hydroxyl group of adjacent nucleotides in RNA, with the intermediary formation of adenosine 2, 3 -cyclic phosphate and splits consequently all secondary phosphate ester bonds of other nucleotides in RNA via the nucleotides 2, 3 -cyclic phopshates. 

Nucleotides join together in nucleic acids by forming a phosphate ester bond between the phosphate group at the 5 end of one nucleotide and the hydroxyl group on the sugar component at the 3 end of another nucleotide (Figure 24.16). 

Fig. 5.3 (a) Phosphonate bond (b) polyphosphate bond (c) phosphate ester bond... 

A phosphate anhydride bond is hydrolyzed and a phosphate ester bond is formed with the C-3 of ribose. 

Enolase catalyzes the dehydration of 2-phosphoglycerate to form phospho-enolpyruvate (PEP). This reaction converts the low-energy phosphate ester bond of 2-phosphoglycerate into the high-energy phosphate bond of PEP. 

When lecithin is hydrolyzed in acidic medium, both the fatty acid ester bonds and the phosphate ester bonds are broken and free fatty acids and inorganic phosphate are released. Using a molybdate test, we can detect the presence of phosphate in the... 

The chemical behavior of DNA is primarily what would be expected on the basis of its structure. The sugar-phosphate backbone is held together by phosphate ester bonds. These bonds are not too different from carboxylic ester bonds. Thus, the phosphodiester... 

Phospholipase D Behavior. While this enzyme shows no stereospecificity in its attack on the ethanolamine phosphoglycerides, its action in releasing free ethanolamine and a phosphatidic acid provides very clear evidence that the ethanolamine was attached to the parent molecule via a phosphate ester bond. Again, the same protocols and enzyme sources illustrated in Chapter 4 for phosphatidylcholine can be applied very easily to the ethanolamine phosphoglycerides. 

Scheme 2 of Fig. 3 shows an elegant way of catalysing the hydrolysis of a phosphate ester [26-28]. Iodosobenzoates, such as the one shown in the figure, are strong nucleophiles and are efficient agents for splitting of phosphate ester bonds. The iodosobenzoate of Fig. 3, Scheme 2 is fully ionised at pH 8 in a microemulsion based on a cationic surfactant. The same hydrolysis rate was obtained at pH 8 in the presence of the iodosobenzoate as at pH 11 in the absence of the... 

Replication of the double strand of DNA. A new strand is assembled on each of the original strands, with the DNA polymerase enzyme forming the phosphate ester bonds of the backbone. 

The following two chemical reactions involve hydrolysis of a phosphate ester bond. 

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