Mazur Type Opa Anhydrolases

Mechanism of hydrolysis of parathion by the opd OPA anhydrase as determined by Lewis et al. The reaction is a single displacement using a base at the active site to activate a water molecule. The activated water attacks the phosphorus, producing diethyl phosphate and 4-nitrophenol. The same active site is able to hydrolyze DFP (Dumas et al. 1989) and related organofluo-rophosphates (Dumas et al. 1990). (Modified after Lewis, V.E., W.J. Donarski, J.R. Wild, and F.M. Raushel. 1988. Biochemistry...

Mazur Type Opa Anhydrase

Note Interestingly, S. cerevisae, Spisula, and T. thermophila do not show a stimulation in DFP hydrolysis with Mn2+. Perhaps, like T. thermophila, the other two species have at least two enzymes, one that hydrolyzes soman and is stimulated by Mn2+. Note Interestingly, S. cerevisae, Spisula, and T. thermophila do not show a stimulation in DFP hydrolysis with Mn2+. Perhaps, like T. thermophila, the other two species have at least two enzymes, one that hydrolyzes soman and is stimulated by Mn2+....

Problem Formulation

The problem formulation component of the risk assessment process is, hopefully, the beginning of an iterative process. This critical step defines the question under consideration and directly affects the scientific validity and policy-making usefulness of the risk assessment. Initiation of the process can begin due to numerous causes such as a request to introduce a new material into the environment, examination of cleanup options for a previously contaminated site, or as a component of...

Biotransformation Detoxification and Biodegradation

As mentioned in the previous chapter, following the entry into a living organism and translocation, a pollutant may be stored, metabolized, or excreted. When the rate of entry is greater than the rate of metabolism and or excretion, storage of the chemical often occurs. However, storage or binding sites may not be the sites of toxic action. For example, lead is stored primarily in the bone, but acts mainly on the soft tissues of the body. If the storage site is not the site of toxic action,...