Biodegradation of atrazine in transgenic plants expressing a modified bacterial atrazine chlorohydrolase (<i>atzA</i>) gene

Wang, Lin; Samac, Deborah A.; Shapir, Nir; Wackett, Lawrence P.; Vance, Carroll P.; Olszewski, Neil E.; Sadowsky, Michael J.

doi:10.1111/j.1467-7652.2005.00138.x

Cited by 84 publications

(24 citation statements)

References 62 publications

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“…Many herbicide-degrading or -detoxifying enzymes, such as the phosphinothricin acetyltransferase Bar (38), bromoxynil-specific nitrilase Bxn (29), 2,4-dichlorophenoxyacetate monooxygenase TfdA (23), and atrazine chlorohydrolase AtzA (36), have been successfully used to construct herbicide-resistant crops. AmpA is a simple homodimer and is able to hydrolyze a variety of amide herbicides to herbicidally inactive products with high hydrolysis efficiency and does not need any cofactor for its activity.…”

Section: Discussionmentioning

confidence: 99%

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

Zhang

Yin

Hang

et al. 2012

Appl Environ Microbiol

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bThe bacterial isolate Paracoccus sp. strain FLN-7 hydrolyzes amide pesticides such as diflubenzuron, propanil, chlorpropham, and dimethoate through amide bond cleavage. A gene, ampA, encoding a novel arylamidase that catalyzes the amide bond cleavage in the amide pesticides was cloned from the strain. ampA contains a 1,395-bp open reading frame that encodes a 465-aminoacid protein. AmpA was expressed in Escherichia coli BL21 and homogenously purified using Ni-nitrilotriacetic acid affinity chromatography. AmpA is a homodimer with an isoelectric point of 5.4. AmpA displays maximum enzymatic activity at 40°C and a pH of between 7.5 and 8.0, and it is very stable at pHs ranging from 5.5 to 10.0 and at temperatures up to 50°C. AmpA efficiently hydrolyzes a variety of secondary amine compounds such as propanil, 4-acetaminophenol, propham, chlorpropham, dimethoate, and omethoate. The most suitable substrate is propanil, with K m and k cat values of 29.5 M and 49.2 s ؊1 , respectively. The benzoylurea insecticides (diflubenzuron and hexaflumuron) are also hydrolyzed but at low efficiencies. No cofactor is needed for the hydrolysis activity. AmpA shares low identities with reported arylamidases (less than 23%), forms a distinct lineage from closely related arylamidases in the phylogenetic tree, and has different biochemical characteristics and catalytic kinetics with related arylamidases. The results in the present study suggest that AmpA is a good candidate for the study of the mechanism for amide pesticide hydrolysis, genetic engineering of amide herbicide-resistant crops, and bioremediation of amide pesticide-contaminated environments.A variety of amide compounds are used as pesticides to control insects, pathogens, and weeds in agriculture. These compounds include benzoylurea insecticides (hexaflumuron, diflubenzuron, etc.), organophosphate insecticides with an amide group (dimethoate, omethoate, etc.), carbamate insecticides or herbicides (carbofuran, carbaryl, propham, chlorpropham, etc.), benzimidazole fungicides (carbendazim, benomyl, etc.), acetanilide herbicides (acetochlor, butachlor, propanil, etc.), substituted phenylurea herbicides (diuron, linuron, etc.), and sulfonylurea herbicides (chlorsulfuron, metsulfuron-methyl, etc.) (33). However, the widespread use of amide pesticides has resulted in the contamination of the environment and agricultural products. Moreover, many amide pesticides are hazardous to human health and may damage crops when used improperly (7,8,33). Thus, the removal of amide pesticides from the environment and agricultural products is of paramount importance.Microorganisms play a significant role in the degradation or detoxification of amide pesticides in the environment. Bacterial strains that are able to degrade amide pesticides (carbofuran, carbaryl, acetochlor, carbendazim, dimethoate, etc.) have been isolated, and their microbial metabolic pathways have also been elucidated (12,22,25,32,43). To date, the sequence information for the following amide pesticide-hydrolyzing enzymes is...

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Section: Discussionmentioning

confidence: 99%

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

Zhang

Yin

Hang

et al. 2012

Appl Environ Microbiol

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“…AtzA has potential utility in both the generation of herbicide-resistant crops (57) and the bioremediation of atrazine contamination. Indeed, Kawahigashi and coworkers have proposed expressing mammalian cytochrome P450 in transgenic plants to phytoremediate atrazine (26,27).…”

Section: Discussionmentioning

confidence: 99%

Catalytic Improvement and Evolution of Atrazine Chlorohydrolase

Scott

Jackson

Coppin

et al. 2009

Appl Environ Microbiol

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The atrazine chlorohydrolase AtzA has evolved within the past 50 years to catalyze the hydrolytic dechlorination of the herbicide atrazine. It is of wide research interest for two reasons: first, catalytic improvement of the enzyme would facilitate its application in bioremediation, and second, because of its recent evolution, it presents a rare opportunity to examine the early stages in the acquisition of new catalytic activities. Using a structural model of the AtzA-atrazine complex, a region of the substrate-binding pocket was targeted for combinatorial randomization. Identification of improved variants through this process informed the construction of a variant AtzA enzyme with 20-fold improvement in its k cat /K m value compared with that of the wild-type enzyme. The reduction in K m observed in the AtzA variants has allowed the full kinetic profile for the AtzA-catalyzed dechlorination of atrazine to be determined for the first time, revealing the hitherto-unreported substrate cooperativity in AtzA. Since substrate cooperativity is common among deaminases, which are the closest structural homologs of AtzA, it is possible that this phenomenon is a remnant of the catalytic activity of the evolutionary progenitor of AtzA. A catalytic mechanism that suggests a plausible mechanistic route for the evolution of dechlorinase activity in AtzA from an ancestral deaminase is proposed.

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“…In addition other hydrolytic processes can give rise to xenobiotic detoxification. For example, a bacterial enzyme atrazine chlorohydrolase, an atrazine-specific enzyme related to melamine deaminase and other amidohydrolases, was shown to confer tolerance to this traizine herbicide when over-expressed in a range of plants including Arabidopsis, alfalfa and tobacco in each case greatly enhanced atrazine resistance (Wang et al 2005). …”

Section: Phase 1 Enzymes -Hydrolasesmentioning

confidence: 99%

New Perspectives on the Metabolism and Detoxification of Synthetic Compounds in Plants

Edwards

Dixon

Cummins

et al. 2010

Plant Ecophysiology

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In attempting to understand the mechanisms by which plants process synthetic compounds we have developed the concept of the 'Xenome', which we define as 'the biosystem responsible for the detection, transport and detoxification of xenobiotics.' In particular the last 10 years have given us unprecedented insights into the proteins responsible for the metabolism and transport of xenobiotics within plant cells and how these systems are regulated. In this review we identify recent advances in our understanding of the xenome and its role in the detoxification and processing of pollutants and pesticides. In particular, we focus on the role of the phase 1 (oxidoreductase/ hydrolytic), phase 2 (bioconjugation), phase 3 (transport) and phase 4 (metabolic recycling) stages of xenobiotic metabolism and the biosensing systems which control their expression. Ultimately, by understanding the capability of the plant xenome to detoxify xenobiotics, we may be able to predict the likely fate and environmental risk of new synthetic compounds entering the environment and food chain.

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Biodegradation of atrazine in transgenic plants expressing a modified bacterial atrazine chlorohydrolase (atzA) gene

Cited by 84 publications

References 62 publications

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

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

Catalytic Improvement and Evolution of Atrazine Chlorohydrolase

New Perspectives on the Metabolism and Detoxification of Synthetic Compounds in Plants

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