Organophosphorus acid anhydrolase

In addition to phosphotriesterase from P. diminuta (PTE) discussed above, two other types of enzymes were found to exhibit phosphotriesterase activity. Interestingly, both are peptidases - the enzymes which in nature hydrolyse a peptide bond. The first one - organophosphorus acid anhydrolase (OPAA) from Alteromonas sp. JD6.5 - is a proline dipeptidase its original activity is to cleave a dipepfide bond with a prolyl residue at the carboxy terminus. The second one - aminopeptidase P (AMPP) from Escherichia coli - is a proline-specific peptidase that catalyses hydrolysis of N-terminal peptide bonds containing a proline residue. ° ... 

The A-esterases now classified as diisopropyl fluorophosphatases (diiso-propyl-fluorophosphate fluorohydrolase, DFPase, somanase, EC 3.1.8.2) were previously listed under EC 3.8.2.1. These enzymes, which hydrolyze P-F and P-CN bonds such as those of nerve gases, should be described as organophosphorus acid anhydrolases rather than phosphatases [56]. Diisopropyl-fluoro-phosphatases exist in different forms with contrasting substrate specificities. One form is able to hydrolyze paraoxon at a low rate, while others have no paraoxonase activity. The different forms differ in their molecular weights and in their requirements for bivalent cations for activity [56]. 

The inactivation and detoxification of paraoxon and congeners are catalyzed by the so-called A-esterases, which, as discussed, comprise aryleste-rase (sometimes still called paraoxonase, EC 3.1.1.2) and phosphoric triester hydrolases (phosphotriesterases, EC 3.1.8) subdivided into aryldialkylphos-phatase (organophosphate hydrolase, paraoxonase, EC 3.1.8.1) and organophosphorus acid anhydrolases (EC 3.1.8.2 see Sect. 9.3.7) [65][69][106-108], These activities, which occur mostly in the mammalian liver and... 

As anhydrides, such compounds are subject to spontaneous hydrolysis, which may contribute to detoxification [160]. Thus, soman hydrolysis at pH 7.5 and 37° occurs with a rate constant of 0.003 - 0.004 min-1 and an activation energy of ca. 55 kJ mol 1 [161]. However, most of the published data refer to enzymatic hydrolysis. Enzymes hydrolyzing P-X anhydride bonds are now known as organophosphorus acid anhydrolases (OPA anhydrolases) classified as EC 3.1.8.2 (also known as diisopropyl-fluorophosphatase, DFPase, tabunase, somanase), an activity related to EC 3.1.8.1 (aryldialkyl-phosphatase, paraoxonase, A-esterase) and formerly classified as EC 3.8.2.1 [64] [65] [69], Much public information on these enzymes can be found in [106],... 

Petrikovics, I., Cheng, T., C., Papahadjopoulos, D., et al., Long circulating liposomes encapsulating organophosphorus acid anhydrolase in diisopropyl-fluorophosphate antagonism, Toxicol. Sci.,57,16-21,2000. 

A few brief notes are added on phosphorofluoridates even though their destruction by microbial activity — although clearly possible — may be limited by their toxicity to the requisite microorganisms. One of the motivations for their inclusion is the fact that the hydrolytic enzyme(s) responsible for defluorination — organophosphorous acid anhydrase (OPA) — is widespread, and is found in a number of bacteria (Landis and DeFrank 1990). The microbial hydrolysis of organophosphorus pesticides and cholinesterase inhibitors is accomplished by several distinct enzymes, all of which are termed organophosphorus acid anhydrolases. These have been reviewed (DeFrank 1991) so that only a few additional comments are justified. 

With this cautionary note in mind, we should note that a related enzyme, prolidase from P. furiosus, has also been reported to be a dicobalt enzyme. In contrast to the aminopeptidases discussed above, prolidase specifically cleaves dipeptides containing a C-terminal proline. Prolidase is present in humans and a variety of bacteria, and appears to be identical to the enzyme previously known as organophosphorus acid anhydrolase, which can hydrolyze and detoxify organophosphorus nerve agents.A function in hydrolyzing peptides, rather than nerve agents that have only been known for a few decades, seems much more probable for these enzymes, which are found in both eukaryotes and prokaryotes. Whether prolidases actually utilize a dinuclear cobalt site in catalysis will require further investigation. 

Nanoencapsulation of Organophosphorus Acid Anhydrolase with Mesoporous Materials for Chemical Agent Decontamination in Organic Solvents... 

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