phosphonates was isolated from B. cereus (La Nauze et al. 1970). One more
interesting enzyme involved in the degradation of phosphonates is C-P lyase refined
from Pseudomonas spp. GLC 11 (Selvapandiyan and Bhatnagar 1994).
Numerous examples of hydrolases with applications in the bioremediation of
pesticide residues include carboxylesterases, phosphotriesterases (Oph and OpdA),
and haloalkane dehalogenases (LinB, AtzA, and TrzN) (Mohn and Tiedje 1992).
Halidohydrolases use water to replace halogens with hydroxyl groups, and this is
affected by the number and types of halogen substituents and by the presence of
unsaturated carbon-carbon bonds. Use of either oxygenases or hydrolases to
dehalogenate pentachlorophenol (PCP) illustrates the potential for microbes to
develop diverse mechanisms for metabolizing such chemicals. A carbofuran
degrading methylotroph strain ER2 initiated the attack on carbofuran by hydrolyzing
the carbamate linkage, producing 7-phenol carbofuran, CO 2 , and methylamine
(Chaudhary and Ali 1988).
2.8.3 Lyases
In the absence of redox cofactors or water, the enzyme lyase catalyzes the cleavage
of bonds, including carbon-carbon bonds such as pyruvate formate-lyase (PFL)
(Sawers 1998) and carbon bonds with phosphorus, oxygen, nitrogen, halides, and
sulfur. The haloelimination reaction catalyzed by lindane hydrochlorinase is active
against the insecticide hexachlorocyclohexane (Nagata et al. 1993) have been linked
to the aminomethyl phosphonic acid (MPA) is susceptible to lyse-producing bacteria
(Zhang et al. 1999), and the use of MPA as a source of phosphorus by Pseudomonas
putida has been observed (Cook et al. 1978). Arthrobacter sp. GLP-1 and Pseudomonas sp. PG2982 degraded glyphosate and produced sarcosine (N-methylglycine)
by C-P lyse activity (Dick and Quinn 1995). Rhizobium meliloti has also been
reported to degrade glyphosate by lyase activity (Park and Hausinger 1995). A
similar pathway has been observed in Arthrobacter atrocyaneus (Pipke and Amrhein
1988) and Flavobacterium sp. (Pipke et al. 1987). Enterobacter cloacae strain K7
possessed C-P lyase activity and degraded glyphosate to sarcosine, which was
subsequently oxidized to glycine (Kryuchkova et al. 2014).
2.8.4 Synthetic Reactions and the Formation of Immobilized
Residues
Synthetic reactions covalently attach pesticide or pesticide transformation products
to other organic molecules. For example, molecules which contain reactive nucleophilic groups, amino (-NH 2 ), hydroxyl (-OH), or carboxyl (-COOH) can participate
in these reactions. Usually, all products of synthetic reactions are larger than the
52
A. Sehrawat et al.
interesting enzyme involved in the degradation of phosphonates is C-P lyase refined
from Pseudomonas spp. GLC 11 (Selvapandiyan and Bhatnagar 1994).
Numerous examples of hydrolases with applications in the bioremediation of
pesticide residues include carboxylesterases, phosphotriesterases (Oph and OpdA),
and haloalkane dehalogenases (LinB, AtzA, and TrzN) (Mohn and Tiedje 1992).
Halidohydrolases use water to replace halogens with hydroxyl groups, and this is
affected by the number and types of halogen substituents and by the presence of
unsaturated carbon-carbon bonds. Use of either oxygenases or hydrolases to
dehalogenate pentachlorophenol (PCP) illustrates the potential for microbes to
develop diverse mechanisms for metabolizing such chemicals. A carbofuran
degrading methylotroph strain ER2 initiated the attack on carbofuran by hydrolyzing
the carbamate linkage, producing 7-phenol carbofuran, CO 2 , and methylamine
(Chaudhary and Ali 1988).
2.8.3 Lyases
In the absence of redox cofactors or water, the enzyme lyase catalyzes the cleavage
of bonds, including carbon-carbon bonds such as pyruvate formate-lyase (PFL)
(Sawers 1998) and carbon bonds with phosphorus, oxygen, nitrogen, halides, and
sulfur. The haloelimination reaction catalyzed by lindane hydrochlorinase is active
against the insecticide hexachlorocyclohexane (Nagata et al. 1993) have been linked
to the aminomethyl phosphonic acid (MPA) is susceptible to lyse-producing bacteria
(Zhang et al. 1999), and the use of MPA as a source of phosphorus by Pseudomonas
putida has been observed (Cook et al. 1978). Arthrobacter sp. GLP-1 and Pseudomonas sp. PG2982 degraded glyphosate and produced sarcosine (N-methylglycine)
by C-P lyse activity (Dick and Quinn 1995). Rhizobium meliloti has also been
reported to degrade glyphosate by lyase activity (Park and Hausinger 1995). A
similar pathway has been observed in Arthrobacter atrocyaneus (Pipke and Amrhein
1988) and Flavobacterium sp. (Pipke et al. 1987). Enterobacter cloacae strain K7
possessed C-P lyase activity and degraded glyphosate to sarcosine, which was
subsequently oxidized to glycine (Kryuchkova et al. 2014).
2.8.4 Synthetic Reactions and the Formation of Immobilized
Residues
Synthetic reactions covalently attach pesticide or pesticide transformation products
to other organic molecules. For example, molecules which contain reactive nucleophilic groups, amino (-NH 2 ), hydroxyl (-OH), or carboxyl (-COOH) can participate
in these reactions. Usually, all products of synthetic reactions are larger than the
52
A. Sehrawat et al.