Sensitivity of a Salmonella typhimurium aspC mutant to sulfometuron methyl, a potent inhibitor of acetolactate synthase II

Dyk, Tina K. Van; LaRossa, Robert A.

doi:10.1128/jb.165.2.386-392.1986

Cited by 30 publications

(29 citation statements)

References 32 publications

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“…The deleterious metabolic consequences of unbalanced ketoacid pools in general are common to all organisms (4,10,20,23,27,30,32,61). We envision YjgF having a broad affinity range and suggest that while YjgF prevents the toxicity of product X, other ␣-ketoacids could be similarly sequestered.…”

Section: Discussionmentioning

confidence: 99%

Reduced Transaminase B (IlvE) Activity Caused by the Lack ofyjgFIs Dependent on the Status of Threonine Deaminase (IlvA) inSalmonella entericaSerovar Typhimurium

2004

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The YjgF/YER057c/UK114 family is a highly conserved class of proteins that is represented in the three domains of life. Thus far, a biochemical function demonstrated for these proteins in vivo or in vitro has yet to be defined. In several organisms, strains lacking a YjgF homolog have a defect in branched-chain amino acid biosynthesis. This study probes the connection between yjgF and isoleucine biosynthesis in Salmonella enterica. In strains lacking yjgF the specific activity of transaminase B, catalyzing the last step in the synthesis of isoleucine, was reduced. In the absence of yjgF, transaminase B activity could be restored by inhibiting threonine deaminase, the first enzymatic step in isoleucine biosynthesis. Strains lacking yjgF showed an increased sensitivity to sulfometruron methyl, a potent inhibitor of acetolactate synthase. Based on work described here and structural reports in the literature, we suggest a working model in which YjgF has a role in protecting the cell from toxic effects of imbalanced ketoacid pools.

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Section: Discussionmentioning

confidence: 99%

Reduced Transaminase B (IlvE) Activity Caused by the Lack ofyjgFIs Dependent on the Status of Threonine Deaminase (IlvA) inSalmonella entericaSerovar Typhimurium

2004

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“…Bacterial cells were allowed to double twice before introduction of the inhibitors, and supplements were added only after inhibition of growth had been confirmed. The supplements included end products and intermediates of the branched-chain amino acid pathway (Val, Ile, Leu, ketoisovalerate, and acetolactate), as well as compounds whose synthesis has been suggested to be affected by high ketobutyrate levels (pantothenate, Met, and Asp) (8,25,46). Inhibition of growth by SMM was partially overcome (doubling time, 2.6 h as opposed to 1.3 h in the absence of inhibitors) by addition of valine.…”

Section: Growth Inhibition As Shown Inmentioning

confidence: 99%

“…As the analog 2-keto-4-hydroxybutyrolactone (compound 3) is a very potent inhibitor of the next enzyme on the coenzyme A pathway, ketopantoate reductase (17), compound 2 might well also be an inhibitor. There have been suggestions that other metabolic fates of ketobutyrate further affect the coenzyme A pool and other biosynthetic activities (24,46). FIG.…”

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Metabolic effects of inhibitors of two enzymes of the branched-chain amino acid pathway in Salmonella typhimurium

1996

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The metabolic effects of inhibitors of two enzymes in the pathway for biosynthesis of branched-chain amino acids were examined in Salmonella typhimurium mutant strain TV105, expressing a single isozyme of acetohydroxy acid synthase (AHAS), AHAS isozyme II. One inhibitor was the sulfonylurea herbicide sulfometuron methyl (SMM), which inhibits this isozyme and AHAS of other organisms, and the other was N-isopropyl oxalylhydroxamate (IpOHA), which inhibits ketol-acid reductoisomerase (KARI). The effects of the inhibitors on growth, levels of several enzymes of the pathway, and levels of intermediates of the pathway were measured. The intracellular concentration of the AHAS substrate 2-ketobutyrate increased on addition of SMM, but a lack of correlation between increased ketobutyrate and growth inhibition suggests that the former is not the immediate cause of the latter. The levels of the keto acid precursor of valine, but not of the precursor of isoleucine, were drastically decreased by SMM, and valine, but not isoleucine, partially overcame SMM inhibition. This apparent stronger effect of SMM on the flux into the valine arm, as opposed to the isoleucine arm, of the branched-chain amino acid pathway is explained by the kinetics of the AHAS reaction, as well as by the different roles of pyruvate, ketobutyrate, and the valine precursor in metabolism. The organization of the pathway thus potentiates the inhibitory effect of SMM. IpOHA has strong initial effects at lower concentrations than does SMM and leads to increases both in the acetohydroxy acid substrates of KARI and, surprisingly, in ketobutyrate. Valine completely protected strain TV105 from IpOHA at the MIC. A number of explanations for this effect can be ruled out, so that some unknown arrangement of the enzymes involved must be suggested. IpOHA led to initial cessation of growth, with partial recovery after a time whose duration increased with the inhibitor concentration. The recovery is apparently due to induction of new KARI synthesis, as well as disappearance of IpOHA from the medium.Enzymes that participate in biosynthetic pathways of essential amino acids have been recognized as targets for a number of safe and effective herbicides (18). The biosynthetic pathway to the branched-chain amino acids valine, leucine, and isoleucine is of special importance in this respect. At least three classes of very potent and extensively used herbicides, the sulfonylureas, the imidazolinones, and the sulfonanilides (26,30,39), are known to inhibit the first common enzyme in this pathway (Fig. 1), acetohydroxy acid synthase (AHAS; EC 4.1.3.18). The second common enzyme in the pathway (Fig. 1), ketol-acid reductoisomerase (KARI; EC 1.1.1.86), is the target for two additional inhibitors with potential herbicidal activity, 2-dimethylphosphinoyl-2-hydroxyacetate (42) and N-isopropyl oxalylhydroxamate (IpOHA) (3).Sulfometuron methyl (SMM), which belongs to the sulfonylurea class of herbicides and inhibits AHAS activity, is an extremely potent herbicide and bacteriostatic age...

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“…In this work, a poxA mutation in Salmonella typhimurium was identified among a set of transposon TnJO-induced sulfometuron methyl (SM)-hypersensitive mutations (42). The herbicide SM is a potent inhibitor of the branched-chain amino acid biosynthetic enzyme acetolactate synthase (24).…”

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confidence: 99%

Pleiotropic effects of poxA regulatory mutations of Escherichia coli and Salmonella typhimurium, mutations conferring sulfometuron methyl and alpha-ketobutyrate hypersensitivity

1987

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A transposon TnlO insertion into the Salmonella typhimurium poxA gene was identified among a set of mutations conferring sulfometuron methyl (SM) hypersensitivity. This TnlO insertion mapped to 95 min on the S. typhimurium chromosome, a location analogous to that of poxA in the Escherichia coli genome. Like the E. coli poxA mutant, this mutant had reduced pyruvate oxidase activity, reduced cross-reacting material to antiserum to purified E. coli pyruvate oxidase, and reduced growth rates. In addition, the following phenotypes were identified for the E. coli and S. typhimurium poxA mutants: hypersensitivity to SM and a-ketobutyrate (AKB), deficiency in AKB metabolism, reduced activity of acetolactate synthase, and hypersensitivity to a wide range of bacterial growth inhibitors, including antibiotics, amino acid analogs, and dyes. An E. coil mutant defective in poxB, the structural gene encoding pyruvate oxidase, did not have these phenotypes; therefore, they are not solely a consequence of a pyruvate oxidase deficiency. Comparisons were made with mutant alleles of two other genes that are located near poxA and confer related phenotypes. The S. typhimurium poxA mutant differed both genetically and phenotypically from an miaA mutant. E. coli abs mutants had somewhat reduced pyruvate oxidase activity but had normal AKB metabolism. The relationship of the pleiotropic phenotypes of the poxA mutants to their SM hypersensitivity is discussed.The pyruvate oxidase of Escherichia coli is a peripheral membrane protein that catalyzes the decarboxylation of pyruvate to acetate via thiamine pyrophosphate, flavin adenine dinucleotide, and Mg2+ as cofactors and requiring terminal electron transport (19). Mutations in two genes affecting pyruvate oxidase activity have been identified. The structural gene for pyruvate oxidase, poxB, is located at 18.7 min on the E. coli genetic map (7). A regulatory gene, poxA, is located at 94 min (6). Enzymological and immunological analyses indicate that mutations in poxA result in a 6-to 10-fold decrease in pyruvate oxidase levels (6, 7). Strains mutated in poxA grow more slowly than poxA+ control strains in both minimal and rich media (6), yet poxB mutants lacking pyruvate oxidase activity grow normally (7).In this work, a poxA mutation in Salmonella typhimurium was identified among a set of transposon TnJO-induced sulfometuron methyl (SM)-hypersensitive mutations (42). The herbicide SM is a potent inhibitor of the branched-chain amino acid biosynthetic enzyme acetolactate synthase (24). S. typhimurium and E. coli K-12 each contain two isozymes of acetolactate synthase. In S. typhimurium, acetolactate synthase isozyme II is sensitive to SM (25), but isozyme I is resistant (26). In E. coli K-12, isozyme III is sensitive while isozyme I is resistant (26). Valine inhibits both isozymes I and III of E. coli K-12 and isozyme I but not isozyme II of S. typhimurium (13). In addition to limiting branched-chain amino acid biosynthesis, SM treatment of S. typhimurium results in the accumulation of a-ke...

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Sensitivity of a Salmonella typhimurium aspC mutant to sulfometuron methyl, a potent inhibitor of acetolactate synthase II

Cited by 30 publications

References 32 publications

Reduced Transaminase B (IlvE) Activity Caused by the Lack ofyjgFIs Dependent on the Status of Threonine Deaminase (IlvA) inSalmonella entericaSerovar Typhimurium

Reduced Transaminase B (IlvE) Activity Caused by the Lack ofyjgFIs Dependent on the Status of Threonine Deaminase (IlvA) inSalmonella entericaSerovar Typhimurium

Metabolic effects of inhibitors of two enzymes of the branched-chain amino acid pathway in Salmonella typhimurium

Pleiotropic effects of poxA regulatory mutations of Escherichia coli and Salmonella typhimurium, mutations conferring sulfometuron methyl and alpha-ketobutyrate hypersensitivity

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