Hydrolase phosphoric monoester

Phosphatases of documented or potential interest in the context of this book include phosphoric monoester hydrolases (EC 3.1.3), phosphoric diester hydrolases (EC 3.1.4), and phosphoric triester hydrolases (EC 3.1.8). 

Phosphatases are numerous and important enzymes (see also Chapt. 2). They are classified as phosphoric monoester hydrolases (phosphatases, EC 3.1.3), phosphoric diester hydrolases (phosphodiesterases, EC 3.1.4), triphosphoric monoester hydrolases (EC 3.1.5), diphosphoric monoester hydrolases (pyrophosphatases, EC 3.1.7), and phosphoric triester hydrolases (EC 3.1.8) [21] [63]. Most of these enzymes have a narrow substrate specificity restricted to endogenous compounds. However, some of these enzymes are active toward xenobiotic organophosphorus compounds, e.g., alkaline phosphatase (EC 3.1.3.1), acid phosphatase (EC 3.1.3.2), aryldialkylphosphatase (para-oxonase (PON1), EC 3.1.8.1) and diisopropyl-fluorophosphatase (tabunase, somanase, EC 3.1.8.2) [64 - 70]. However, such a classification is far from definitive and will evolve with further biochemical findings. Thus, a good correlation has been found in human blood samples between somanase and sarinase activities on the one hand, and paraoxonase (PON1) type Q isozyme concentrations on the other [71]. 

Firestone and Heath442 found that the alkaline phosphatase (ortho-phosphoric monoester phosphate hydrolase, EC 3.1.3.1) that is induced in cultured cells by dibutanoy 1-cAMP is not detectable in the presence of inhibitors of glycosylation, although messenger RNA is found in proportions that are comparable to those of noninhibited... 

In a classification from 1992 (International Union of Biochemistry, 1992) hydrolases of OP were described as a special entity as phosphoric triester hydrolases which comprise three groups of enzymes phosphoric monoester hydrolases (EC 3.1.3), phosphoric diester hydrolases (EC 3.1.4), and phosphoric triester hydrolases (phosphotriesterases) (EC 3.1.8). Phosphoric triester hydrolases are further divided in two similar subgroups aryldialkylphos-phatases (EC 3.1.8.1) and diisopropylfluorophosphatases (EC 3.1.8.2). 

A/B Phosphatases Phosphoryl group transfer from a phosphoric monoester to water as an acceptor molecule. (Phosphoric monoesters are cleaved hydrolytically). 3.1.3. 3.6.1. Phosphoric ester hydrolases Hydrolases acting on acid anhydrides in phosphorous-containing anhydrides... 

NUCLEOTIDASES AND RELATED ENZYMES - PHOSPHORIC MONOESTER HYDROLASES... 

Enzyme assays based on inhibition effects are not as commonly employed as substrate determinations. but one or two are very important. Preeminent is the determination of organophosphorus compounds by using their inhibitory effect on cholinesterase enzymes (E.C. 3.1.1.8—the first digit signifies a hydrolase enzyme, the second that the compounds hydrolyzed are esters, and the third that they are phosphoric monoesters). The latter catalyze the conversion of acylcholines to choline and the corresponding acid ... 

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