Phosphomonoesterases substrate-specific

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... 

Plant phytases have all of the characteristics of a nonspecific acid phosphomonoesterase with broad substrate specificity (73). 

This enzyme is a non-specific phosphomonoesterase that shows maximum activity at pH values greater than 8.569 It also catalyzes the transfer of phosphoryl groups. These reactions involve the formation of a phosphoseryl intermediate and the hydrolyzed substrate. The phosphoenzyme may transfer the phosphoryl group to water or to an acceptor molecule to give a new phosphoester (equations 19 and 20, where E—P represents the covalently bound phosphoenzyme and E-P a non-covalent complex, in which phosphate is coordinated to the zinc). The phosphoenzyme may be formed from either direction. 

The phosphomonoesterases that proved most useful in this work, although free of proteolytic impurities, were found to be complex in their behavior toward phosphate esters. As indicated in Table II, if tested with the aid of low molecular weight substrates, the intestinal (85) and the potato phosphatase (34) act on 0—P and N—P bonds, whereas the prostate enzyme (86) hydrolyzes only 0—P linkages. After the discovery of the specificity of two of these enzymes for low molecular weight N—P esters, it was noticed that the intestinal enzyme, although classified in the literature as alkaline phosphatase, hydrolyzes N—P bonds both at pH 5.6 and 9.0, but not at pH 7.0. Since the pH range of 5 to 6 is that of maximum stability of almost all proteins, most experiments were carried out in this pH range. Thus the use of these three enzymes, either alone or in combination with each other, proved to be quite a powerful tool. 

Enzymatic reactions can be used as a means of both characterizing and releasing classes of organic phosphorus present in waters, soils and sediments. For example, phosphate monoesters can be quantified by the use of a phosphomonoesterase such as alkaline phosphatase. Alternately, the high specificity of some enzymes for particular substrates can be used as the basis for determination of specific organic phosphorus compounds, or as part of a post-separation quantification step. 

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