OPA anhydrolases

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],... 

Comparison of Several Aquatic OPA Anhydrase Activities with Typical Squid and Mazur-Type OPA Anhydrolases... 

Characteristics of the opd Gene Product and Other Bacterial OPA Anhydrolases... 

Currently under intense scrutiny, the protein product of the opd gene of Psuedomonas diminuta is perhaps the best studied of the bacterial OPA anhydrolases. It has been shown that the opd OPA anhydrase (also called... 

Clearly, there is a diversity of related and unrelated OPA anhydrolases found in bacteria. The opd and opdA genes are obviously related sequences and share a common evolutionary ancestor. The OPAA2 enzyme is apparently quite different. The selection pressure resulting in enzymes with similar activities but quite different structure is not known. This situation mimics the situation in eukaryotic organisms where at least two very different enzymes are capable of hydrolyzing organophosphates. 

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. 

Other name(s) DFPase tabunase somanase organophosphorus add anhydrolase organophosphate acid anhydrase OPA anhydrase diisopropylphosphofluoridase dialkylfluorophosphatase diisopropyl phosphorofluoridate hydrolase isopropylphosphorofluoridase diisopropylfluorophosphonate dehalogenase... 

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