Cloning of a Novel Aldo-Keto Reductase Gene from Klebsiella sp. Strain F51-1-2 and Its Functional Expression in Escherichia coli

Abstract

A soil bacterium capable of metabolizing organophosphorus compounds by reducing the PAS group in the molecules was taxonomically identified as Klebsiella sp. strain F51-1-2. The gene involved in the reduction of organophosphorus compounds was cloned from this strain by the shotgun technique, and the deduced protein (named AKR5F1) showed homology to members of the aldo-keto reductase (AKR) superfamily. The intact coding region for AKR5F1 was subcloned into vector pET28a and overexpressed in Escherichia coli BL21(DE3). Recombinant His 6 -tagged AKR5F1 was purified in one step using Ni-nitrilotriacetic acid affinity chromatography. Assays for cofactor specificity indicated that reductive transformation of organophosphorus compounds by the recombinant AKR5F1 specifically required NADH. The kinetic constants of the purified recombinant AKR5F1 toward six thion organophosphorus compounds were determined. For example, the K m and k cat values of reductive transformation of malathion by the purified recombinant AKR5F1 are 269.5 ؎ 47.0 ⌴ and 25.7 ؎ 1.7 min ؊1 , respectively. Furthermore, the reductive transformation of organophosphorus compounds can be largely explained by structural modeling.Synthetic organophosphorus (OP) compounds are widely used in agriculture to control major insect pests. These compounds have been implicated in several nerve and muscular diseases in human beings. Microbial degradation of OP pesticide has become the focus of many studies because it is economical and effective (30). The most widely studied bacterial enzyme for OP detoxification is the OP hydrolase (OPH). OPH has been isolated from several bacteria (23,29), and the OPH from Pseudomonas diminuta has the widest range of substrate specificity (6). A similar enzyme, OPH A (OPDA), has been isolated from Agrobacterium radiobacter and was found to have 90% homology to OPH at the amino acid level (16). However, the rates of hydrolysis by OPH differ dramatically for members of the OP compound family, ranging from the diffusion-controlled limit for hydrolysis of paraoxon to several orders of magnitude slower for malathion, chlorpyrifos, and VX (6).Various attempts have been made to isolate malathion-degrading microorganisms. Matsumura et al. isolated a malathiondegrading fungus, Trichoderma viride, and a bacterium, Pseudomonas sp., from contaminated soil, which rapidly degrades malathion through carboxylesteratic hydrolysis as well as desmethylation processes (22). Lewis et al. isolated a fungus, Aspergillus oryzae, from a freshwater pond, which transforms malathion to ␤-malathion monoacid and malathion dicarboxylic acid, indicating the presence of carboxylesteratic hydrolysis activity (19). Degradation of malathion by other bacterial species was also reported (11). Although many studies have been carried out on the microbial degradation of malathion, there is a lack of information on the genetic and enzymatic aspects in the degradation of malathion.The aldo-keto reductases (AKRs) are a growing superfamily of approximately 120 enzymes, currently...

Cloning of a Novel Arylamidase Gene from Paracoccus sp. Strain FLN-7 That Hydrolyzes Amide Pesticides

“…OPH is a member of the amidohydrolase superfamily that can hydrolyze the POO, POF, and POS bonds of organophosphate pesticides (14). Reduction of the PAS group by an aldo-keto reductase (AKR5F1) was another reported degradation pathway for dimethoate (15). The present study suggests that AmpA employs a different metabolic mechanism: hydrolysis of the amide bond to yield dimethoate carboxylic acid.…”

“…For pH stability determination, the enzyme was preincubated in buffer at pH 3 to 11 at 35°C for 1 h, and then the remaining activity was assayed. The optimal reaction temperature was determined under standard conditions at pH 7.5 and different temperatures (15,20,25,30,35,40,45, 50, 55, 60, and 70°C). For determination of the thermostability, the enzyme was preincubated in a water bath at different temperatures (40, 50, 60, 70, and 80°C) for 1 h, and then the remaining activity was assayed.…”

Co-metabolic degradation of dimethoate by Raoultella sp. X1

“…Although many bacteria were found to be able to degrade dimethoate (Deshpande et al 2001;Liu et al 2001a;Jiang et al 2007;Debmandal et al 2008), only two enzymes responsible for dimethoate degradation have been so far identified and purified from Aspergillus niger ZHY256, and Klebsiella sp. strain F51-1-2 (Liu et al 2001a;Jiang et al 2007). As one of midtoxicity OP pesticides, dimethoate has been widely used against pests on rice, potato, cabbage, and cotton with a yearly output of 10 kt in China.…”

Bioinformatic Identification of Aldo-Keto Reductase from Newly Isolated Arthrobacter nicotianae strain PR and Its Phylogenetic Analysis Among Soil Bacteria

“…Earlier reports indicate that several microorganisms such as Pseudomonas spp., Trichoderma viridae, Aspergillus oryzae etc can degrade or involved in the detoxification of carbonyl group-containing xenobiotics and can metabolize many endogenous intermediate products, such as aldehydes, ketones, exogenous compounds like plant phytoallexins, toxins, and anthropogenic chemicals in the environment [3]. The role of AKR has been noticed earlier in bacteria like Bacillus subtilis and Escherichia coli.…”

“…Both prokaryotes, especially the soil bacteria, and a range of eukaryotes carry such metabolic enzyme Aldo-Keto Reductase genes commonly called AKR. Such defensive enzymatic mechanisms include (i) reductive metabolism of biogenic and xenobiotic materials to primary and secondary alcohols, as well as (ii) alternative biosynthetic metabolism for essential nutrient absorption [3].…”