Orthophosphate monoesters

Alkaline phosphatases form a widespread group of relatively unspecific enzymes catalyzing the hydrolysis of many orthophosphate monoesters. Their pH optima are generally at pH 8 or above. Several alkaline phosphatases have been shown to contain zinc (3). 

Acid Phosphatase Orthophosphate monoester + H20 —> an alcohol + orthophosphate. 

Hydrogen-1. Bases such as phosphites deshield the acidic proton of phenols, alcohols, and chloroform. Exceptions are bases like pyridine, which have a large magnetic anisotropy. One possible explanation is that the shift is due primarily to the distortion of charge around the proton produced by the donor s lone pair of electrons. The reactivity of orthophosphate monoesters to hydrolysis was related to 5qh of the protonated leaving group. Further work has been completed on the stereochemical assignments of substituted... 

Add phosphatases are ubiquitously distributed enzymes defined by the pH optimum (usually 4.9-6.0) of their hydrolytic activity toward orthophosphate monoesters. A metal-dependent subclass of these enzymes was first recognized in 1973, when iron-bearing acid phosphatases were isolated from porcine uterine fluid and bovine spleen Because of their intense colors they have become known as the purple add phosphatases. Its source, content of iron, and presumed role in iron transport fix>m pregnant sow to fetal pig have earned the pordne protein the euphonious name of uteroferrin. 

Sodium hydroxide is the most effective extractant of soil P but its use inevitably causes changes to soil organic matter, including the hydrolysis of alkali-labile P like RNA, phospholipids and phosphonolipids. In one soil, myo-inositol hexakisphosphate was confirmed as the main orthophosphate monoester. ... 

Some of the more readily mineralised forms of P in a soil development sequence were recently identified by a P-nmr technique . Orthophosphate diesters, including phospholipids, and phosphonates, but not orthophosphate monoesters, appeared able to supply plant-available P in these mainly undisturbed New Zealand tussock grassland ecosystems, given soil and climatic conditions favourable to P mineralisation. Similarly, orthophosphate diesters were more readily mineralised than monoesters in an old grassland soil after 21 y of bare fallowing, because the diesters declined sharply during this period. ... 

This enzyme [EC 3.1.3.1], also known as alkaline phos-phomonoesterase, phosphomonoesterase, and glycero-phosphatase, catalyzes the hydrolysis of many ortho-phosphoric monoesters (the substrate specificity is quite wide) to generate an alcohol and orthophosphate. The... 

Acid phosphatase or orthophosphoric monoester phosphohydrolase (EC 3.1 3.2) activity is widespread throughout nature. Hydrolysis of a variety of orthophosphate esters as well as transphosphorylation reactions are catalyzed by enzymes from many sources. Table I illustrates their ubiquitous nature. 

Figure 11.2 Dominant groups of P found in DOP (phosphonates, phosphate monoesters, orthophosphate, phosphate diesters, pyrophosphates, and tri- and tetrapolyphosphates) in oceanic waters. (Modified from Kolowith et al. 2001.)...

Although the characterization of DOP in rivers and estuaries has been largely ignored, some work in the Mississippi River indicated that the composition of SNP primarily consisted of diester and monoester phosphates, phosphonates, orthophosphates, and/or tri- and tetrapolyphosphates. 

Alkaline phosphatase (E.C.3.1.3.1) is also used in many enzyme-amplified immunoassays. It catalyzes the hydrolysis of an orthophosphoric monoester, to produce an alcohol and orthophosphate. This 100 kDa enzyme has a pH optimum near 9, and exhibits activities of 1000 U/mg (37 °C). With p-nitropheny I phosphate as substrate, the p-nitrophenol produced may be monitored at 450 nm (Eq. 6.11) ... 

Certain dipositive metal ions not only accelerate the hydrolysis of ATP, as mentioned above, but also assist in the transfer of a phosphoryl group from one molecule to another. Such a nonenzymatic transphosphorylation takes place between ATP and an orthophosphate ion or its monoester in the presence of calcium(II), cadmium(II), and manganese(II). This type of nonenzymatic process can serve as a model for the biologically important enzymatic transphosphorylations that involve ATP, although... 

Phosphorns is a major constituent of macromolecules, particularly in nncleic acids (DNA and RNA), in phospholipids of membranes, and as monoesters of a variety of compounds, particularly those involved in biochemical pathways. In growing microorganisms, more than half of the organic phosphorus is in nncleic acids, whereas phospholipids and monoesters constitute the remainder in varying proportions (Table 9.3 Magid et al., 1996). Many organisms can store orthophosphate or polyphosphates. In plants, IHP can form a major storage componnd for phosphorus, particularly in seeds. 

Many organisms can store orthophosphate or polyphosphates. In plants, inositol hexaphos-phate (IHP) can form a major storage compound for phosphorus, particularly in seeds. Although relatively low in concentration, diesters may contribute to short-term bioavail-able pool more than monoesters. Compared to monoesters, diesters are more accessible to microbial attack. This fraction was shown to be rapidly made available to plants. 

I) Phosphomonocsterases. It is well known that both acid and alkaline phospho-monoesterases (orthophosphoric monoester phosphohydrolase EC 3.1.3.1 and EC 3.1.3.2) are widely distributed in nature. These enzymes are able to split glycerophosphate formed by the action of GPC diesterase (Reaction 39) into glycerol and orthophosphate ... 

Figure 22 shows the pho hate profiles of freeze-dried saliva resuspended in a buffer solution. The top spectrum was obtained from a patient with a history of dental caries and relatively good oral hygenic habits. The principal signal arises from salivary inorganic orthophosphate. The other resonances arise from various phosphomono- and diesters. The monoester resonance band appears at 3.95 ppm and corresponds to approximately 43% of the... 

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