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Csaba Cseke - One of the best experts on this subject based on the ideXlab platform.
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lack of cross resistance of imazaquin resistant xanthium strumarium Acetolactate Synthase to flumetsulam and chlorimuron
Plant Physiology, 1993Co-Authors: Paul R Schmitzer, Robert J Eilers, Csaba CsekeAbstract:Acetolactate Synthase (ALS) was isolated from a field population of cocklebur (Xanthium strumarium) that developed resistance to the herbicide Scepter following three consecutive years of application. The active ingredient of Scepter, imazaquin, gave an inhibitor concentration required to produce 50% inhibition of the enzyme activity that was more than 300 times greater for the resistant enzyme than for the wild-type cocklebur ALS. Tests with flumetsulam and chlorimuron show that the resistant ALS was not cross-resistant to these two other classes of ALS inhibitors.
Jung Do Choi - One of the best experts on this subject based on the ideXlab platform.
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amino acid residues conferring herbicide tolerance in tobacco Acetolactate Synthase
Biochemical and Biophysical Research Communications, 2000Co-Authors: Chom-kyu Chong, Jung Do ChoiAbstract:Acetolactate Synthase (ALS) is the common enzyme in the biosynthetic pathways leading to valine, leucine, and isoleucine in plants and microorganisms. ALS is the target site of several classes of structurally unrelated herbicides including sulfonylureas, imidazolinones, and triazolopyrimidines. To identify the residues conferring herbicide tolerance in tobacco ALS, site-directed mutagenesis for three residues, Ala121, Pro187 and Ser652, was performed. Mutant A121T showed strong resistance to Londax (a sulfonylurea) and Cadre (an imidazolinone), while mutant S652T was resistant only to Cadre. The S652N mutation abolished the binding affinity of FAD, and inactivated the enzyme. Double mutation of Ala121 and Ser652 with Thr yielded a mutant highly tolerant to Londax, Cadre, and TP (a triazolopyrimidine sulfonamide), but has enzymatic properties similar to those of wild-type. Substitution of Pro187 with Ser resulted in the enzyme highly susceptible to oxidation and fragmentation. These results suggest that two residues Ala121 and Ser652 are potent residues conferring herbicide resistance in tobacco ALS, and that double mutation of Ala121 and Ser652 by Thr can confer stronger tolerance to Londax, Cadre, and TP.
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Role of Tryptophanyl Residues in Tobacco Acetolactate Synthase
Biochemical and biophysical research communications, 1999Co-Authors: Chom-kyu Chong, Hee-jee Shin, Soo-ik Chang, Jung Do ChoiAbstract:Abstract Acetolactate Synthase (ALS) catalyzes the first common step in the biosynthesis of valine, leucine, and isoleucine. ALS is the target of three classes of herbicides, the sulfonylureas, the imidazolinones, and the triazolopyrimidines. Five mutants (W266F, W439F, W490F, W503F, and W573F) of the ALS gene from Nicotiana tabacum were constructed and expressed in Escherichia coli, and the enzymes were purified. The W490F mutation abolished the binding affinity for cofactor FAD and inactivated the enzyme. The replacement of Trp573 by Phe yielded a mutant ALS resistant to the three classes of herbicides. The other three mutations, W266F, W439F, and W503F, did not significantly affect the enzymatic properties and the sensitivity to the herbicides. These results indicate that the Trp490 residue is essential for the binding of FAD and that Trp573 is located at the herbicide binding site. The data also suggest that the three classes of herbicides bind ALS competitively.
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Inhibition of Barley Acetolactate Synthase by Triazolopyrimidine Derivative
Journal of The Korean Chemical Society, 1999Co-Authors: Sung Ho Kim, Soo-ik Chang, Sung Keon Namgoong, Jung Hyu Shin, Jung Do ChoiAbstract:Acetolactate Synthase (ALS) catalyzes the first common reaction in the biosynthesis of branched-chain amino acids, valine, leucine, and isoleucine. ALS is the common target of several classes of structurally diverse herbicides, the triazolopyrimidines, the imidazolinones, the sulfonylureas, and pyrimidyl-oxy-benzoates. We examined ihibitory activities of newly synthesized triazolopyrimidine sulfonamide derivatives using partially purified ALS from barley. values for the active derivatives are 0.5nM∼8M. Among them TP1 and TP2 are the most potent ALS inhibitors with values of 0.5nM and 1.6nM, respectively. These inhibitors are more potent in the inhibition of barley ALS than commercial herbicides, Metosulam (;3.6 nM), Flumetsulam (;126 nM), and Cadre (). The progress curves for inhibition of ALS by TP2 showed that the amount of inhibition increases with time. The inhibition of ALS by TP2 was mixed-type inhibition with respect to pyruvate. Dual inhibition analyses of TP2 versus an imidazolinone, Cadre, and Leu showed parallel and intercepting kinetic pattern, respectively. The results suggest that TP2 binds to ALS competively with Cadre but not with Leu. Chemical modification of cysteinly residues in ALS decreased the sensitivity of ALS to Leu, while the modification did not affect the sensitivity of ALS to TP2 and Cadre.
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Functional Amino Acid Residues of Recombinant Tobacco Acetolactate Synthase
Journal of Biochemistry and Molecular Biology, 1998Co-Authors: Chom-kyu Chong, Soo-ik Chang, Jung Do ChoiAbstract:Acetolactate Synthase (ALS) is the common enzyme in the biosynthetic pathways leading to leucine, valine, and isoleucine. Tobacco ALS was expressed in E. coli and purified to homogeneity. The recombinant tobacco ALS was inactivated by thiol-specific reagents, N-ethylmaleimide (NEM) and 5,5'-dithio-bis-(2-nitrobenzoic acid) (DTNB). Inactivation of the ALS by NEM followed pseudo-first order kinetics and was first order with respect to the modifier. The substrate pyruvate protected the enzyme against the inactivation by NEM and DTNB. Extrapolation to complete inactivation of the enzyme by DTNB showed modification of approximately 2 out of 4 total cysteinyl residues (or 2 cysteinyl and 1 cysteinyl residues), with approximately 1 residue protected by pyruvate. The tobacco ALS was also inactivated by the tryptophanspecific reagent, N-bromosuccinimide (NBS), and was similarly protected by pyruvate. The kinetics of the inactivation was first-order with respect to NBS. The present data suggest that cysteinyl and tryptophanyl residues play a key role in the catalytic function of the enzyme.
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Overexpression of Nicotiana tabacum Acetolactate Synthase as an Inducible Fusion Protein in Escherichia coli: Production of a Polyclonal Antibody to Nicotiana tabacum Acetolactate Synthase
Journal of Biochemistry and Molecular Biology, 1996Co-Authors: Soo-ik Chang, Jung Do Choi, Moon-kyeong Kang, Hyun-ju Kim, Sung Keon NamgoongAbstract:Acetolactate Synthase (ALS, EC 4.1.3.18) is the first common enzyme in the biosynthesis of leucine, isoleucine, and valine. It is the target enzyme for several classes of herbicides, including the sulfonylureas, the imidazolinones, the mazolopyrimidines, the pyrimidyl-oxy-benzoates, the pyrimidyl-thio-benzens, and the 4,6-dimethoxypyrimidines. An amino-terminal fragment of the sulfonylurea-resistant ALS gene (SurB) from Nicotiana tabaccum was cloned into the bacterial expression vector pGEX-2T. The resulting recombinant plasmid pGEX-ALS1 was used to transform Escherichia coli strain BL21, and the tobacco ALS was expressed in the bacteria as a protein fused with glutathione S-transferase (GST). Polyclonal antibodies against the fusion product (GST-ALS) were produced, and the sensitivity of GST-ALS with the rabbit anti-GST-ALS IgG was up to 50 ng. This antibody was used for Western blot analysis of the partially purified ALS from barley shoots. The results suggest that the polyclonal antibody produced in this study can be used to detect plant ALS.
Peter Böger - One of the best experts on this subject based on the ideXlab platform.
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The oxygenase reaction of Acetolactate Synthase detected by chemiluminescence
FEBS letters, 1994Co-Authors: Jörg Durner, Valérie Gailus, Peter BögerAbstract:In addition to the synthesis of ketolacids the enzyme Acetolactate Synthase shows an oxygen-consuming side reaction. Partially purified Acetolactate Synthase from corn (Zea mays L.) and barley (Hordeum vulgare L.) exhibits chemiluminescence in the presence of oxygen, Mn" and low concentrations of pyruvate. Light emission is inhibited by azide, but not by catalase or superoxide dismutase. The data suggest the formation of singlet oxygen during the catalytic cycle, and provides a basis for a highly sensitive assay for the oxygenase reaction of Acetolactate Synthase. Both Synthase activity and chemiluminescence are inhibited by sulfonylurea herbicides. The results add a new aspect to the irreversible inhibition of Acetolactate Synthase by these herbicides which may be enhanced by the presence of reactive oxygen species.
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new aspects on inhibition of plant Acetolactate Synthase by chlorsulfuron and imazaquin
Plant Physiology, 1991Co-Authors: Jörg Durner, Valérie Gailus, Peter BögerAbstract:The sulfonylurea herbicide chlorsulfuron and the imidazolinone herbicide imazaquin were shown to be noncompetitive and uncompetitive inhibitors, respectively, of purified Acetolactate Synthase from barley (Hordeum vulgare L.) with respect to pyruvate. From double-reciprocal plots of the time-dependent biphasic inhibition by chlorsulfuron, an initial apparent inhibition constant of 68 nanomolar was calculated (a 0 to 4 minute assay was used for the initial inhibition), and a final steady-state dissociation constant of 3 nanomolar was estimated. The corresponding constants for imazaquin were 10 and 0.55 micromolar. Specific binding of [14C]chlorsulfuron and [14C]imazaquin to purified Acetolactate Synthase from barley and partially purified enzyme from corn (Zea mays L.) could be demonstrated by gel filtration and equilibrium dialysis. Evidence is presented that the binding of the inhibitors to the enzyme follows the previously described mechanism of slow reversibility once excess inhibitor has been removed. However, after formation of the slowly reversible complex and subsequent dissociation, both chlorsulfuron and imazaquin seem to permanently inactivate Acetolactate Synthase. These results add a new feature to the mode of action of these herbicides with respect to their high herbicidal potency.
M. Paula Watt - One of the best experts on this subject based on the ideXlab platform.
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Agronomic evaluation and molecular characterisation of the Acetolactate Synthase gene in imazapyr tolerant sugarcane (Saccharum hybrid) genotypes
Plant Cell Reports, 2018Co-Authors: M.j. Koetle, Varnika Singh, S. J. Snyman, R. Stuart Rutherford, Dyfed Lloyd Evans, M. Paula WattAbstract:Key message Mutagenesis had no effect on number of stalks/plot, stalk height, fibre and sucrose content of mutants. Imazapyr tolerance is likely due to a S622N mutation in the Acetolactate Synthase gene. Abstract The herbicidal compound imazapyr is effective against weeds such as Cynodon and Rottboellia species that constrain sugarcane production. This study aimed to compare agronomic characteristics of three imazapyr tolerant mutants (Mut 1, Mut 6 and Mut 7) with the non-mutated N12 control after 18 months of growth, and to sequence the Acetolactate Synthase ( ALS ) gene to identify any point mutations conferring imazapyr tolerance. There were no significant differences in the number of stalks/plot, stalk height, fibre and sucrose contents of the mutants compared with the N12 control. However, Mut 1 genotype was more susceptible to the Lepidopteran stalk borer, Eldana saccharina when compared with the non-mutated N12 (11.14 ± 1.37 and 3.89 ± 0.52% internodes bored, respectively), making Mut 1 less desirable for commercial cultivation. Molecular characterisation of the ALS gene revealed non-synonymous mutations in Mut 6. An A to G change at nucleotide position 1857 resulted in a N513D mutation, while a G to A change at nucleotide position 2184 imposed a S622N mutation. Molecular dynamics simulations revealed that the S622N mutation renders an asparagine side chain clash with imazapyr, hence this mutation is effective in conferring imazapyr tolerance.
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Agronomic evaluation and molecular characterisation of the Acetolactate Synthase gene in imazapyr tolerant sugarcane (Saccharum hybrid) genotypes.
Plant cell reports, 2018Co-Authors: M.j. Koetle, Dyfed Lloyd Evans, Varnika Singh, S. J. Snyman, R. Stuart Rutherford, M. Paula WattAbstract:Key message Mutagenesis had no effect on number of stalks/plot, stalk height, fibre and sucrose content of mutants. Imazapyr tolerance is likely due to a S622N mutation in the Acetolactate Synthase gene.
Paul R Schmitzer - One of the best experts on this subject based on the ideXlab platform.
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lack of cross resistance of imazaquin resistant xanthium strumarium Acetolactate Synthase to flumetsulam and chlorimuron
Plant Physiology, 1993Co-Authors: Paul R Schmitzer, Robert J Eilers, Csaba CsekeAbstract:Acetolactate Synthase (ALS) was isolated from a field population of cocklebur (Xanthium strumarium) that developed resistance to the herbicide Scepter following three consecutive years of application. The active ingredient of Scepter, imazaquin, gave an inhibitor concentration required to produce 50% inhibition of the enzyme activity that was more than 300 times greater for the resistant enzyme than for the wild-type cocklebur ALS. Tests with flumetsulam and chlorimuron show that the resistant ALS was not cross-resistant to these two other classes of ALS inhibitors.