The application of pesticides has facilitated the
development and expansion of agriculture globally. Organophosphates belong to a
class of highly toxic neurotoxins that are commonly used as insecticides and
chemical warfare agents (Surekha Rani et al. 2008).
The continuous use of organophosphates in intensive quantities throughout the
world and their potential neurotoxicity to humans has led to the development of
various efficient and safe bioremediation strategies to deal with their wide
dispersal in the ecosystem. Enzymatic degradation by organophosphorus hydrolase
(OPH) has received considerable attention since it provides the possibility of
both eco friendly and in situ detoxification (Catherine et al. 2002). The
focus of this work is organophosphorus hydrolase (OPH, E.C. 18.104.22.168), which
catalyzes the hydrolysis of many organophosphorus compounds and greatly reduces
the toxicity and even can completely mineralize them.
Identical opd genes coding for OPH were found
in two soil microorganisms, Pseudomonas diminuta MG and Flavobacterium
sp. (Sethunathan et al. 1998). Although
OPH hydrolyzes a wide range of organophosphates, the effectiveness of
hydrolysis varies dramatically. Widely used organophosphorus insecticides like
methyl parathion, chlorpyrifos, and diazinon are hydrolyzed 30 to 1,000 times
slower than is the preferred substrate, paraoxon. This reduction in catalytic
rate is due to the unfavorable interaction of these substrates with the active
sites involved in catalysis and/or structural functions (Zheng et al. 2013).
A number of enzymes are capable of hydrolysing a
broad range of OP triesters into less or non-toxic compounds. These enzymes are
possible bioremediators because of their ability to decontaminate OP-containing
waters and soils. The most thoroughly characterized phosphotriesterases have
been isolated from Flavobacterium sp. ATCC 27551, Pseudomonas
diminuta (OPH) and Agrobacterium radiobacter (OpdA) (Fernanda et al.
2010). These enzymes belong to the binuclear
metallohydrolase family and share high sequence and structural homology.
Phosphotriesterases are highly promiscuous enzymes, hydrolysing a large range
of substrates. The mechanism of phosphotriester hydrolysis by OPH has been
studied extensively (Castro et al. 2016). In
a proposed reaction scheme based largely on crystal structures with bound
inhibitors, the phosphoryl oxygen of the substrate binds to the ?-metal
ion (Janet et al.2005).
In the present research focuses on the
interaction and degradation of chlorpyrifos by OPH enzyme, as this is
responsible for detoxification. The molecular docking study was conducted under
FlexX docking software package.