Acetolactate synthase gene

Haughn, G., Smith, J., Mazur, B. Sommerville, C. (1988). Transformation with a mutant Arabidopsis acetolactate synthase gene renders tobacco resistant to sulfonylurea herbicides. Molecular and General Genetics 211, 266-71. 

Aristidou, A.A. San, K.Y. Bennett, G.N. Modification of central metabolic pathway in Escherichia coli to reduce acetate accumulation by heterologous expression of the Bacillus subtilis acetolactate synthase gene. Biotechnol. Bioeng. 1994, 44 (8), 944-951. 

Herbicide-Resistant Plants Carrying Mutated Acetolactate Synthase Genes... 

FIGURE 2 Amino acid conservation between acetolactate synthase genes. The numbers indicate amino acid residues. The first bar represents a comparison of the deduced amino acid sequences of ALS from tobacco and Arabidopsis-, the second bar represents a comparison between the amino acid sequences of the three E. coli ALS isozymes. Regions of conservation are shown in white. 

Acetolactate synthase inhibition by imidazolinones and triazolopyrimidines, 460 sensitivity to sulfonylurea herbicides, 460 Acetolactate synthase gene activity and inheritance of resistance in tobacco, 461... 

Table III. Acetolactate Synthase Gene-Enzyme Relationships...

As indicated in Fig. 24-17, pyruvate is the starting material for the formation of both l- and D-alanine and also the branched chain amino acids valine, leucine, and isoleucine.339,340 The chemistry of the reactions has been discussed in the sections indicated in the figure. The first step is catalyzed by the thiamin diphosphate-dependent acetohydroxyacid synthase (acetolactate synthase), which joins two molecules of pyruvate or one of pyruvate and one of 2-oxobutyrate (Fig. 24-17 Fig. 14-3).340a b In E. coli there are two isoenzymes encoded by genes ilv B and ilv HI. Both are regulated by feedback inhibition by valine, probably... 

Although the utility of transaminases has been widely examined, one such limitation is the fact that the equilibrium constant for the reaction is near unity. Therefore, a shift in this equilibrium is necessary for the reaction to be synthetically useful. A number of approaches to shift the equilibrium can be found in the literature.53 124135 Another method to shift the equilibrium is a modification of that previously described. Aspartate, when used as the amino donor, is converted into oxaloacetate (32) (Scheme 19.21). Because 32 is unstable, it decomposes to pyruvate (33) and thus favors product formation. However, because pyruvate is itself an a-keto acid, it must be removed, or it will serve as a substrate and be transaminated into alanine, which could potentially cause downstream processing problems. This is accomplished by including the alsS gene encoding for the enzyme acetolactate synthase (E.C. 4.1.3.18), which condenses two moles of pyruvate to form (S)-aceto-lactate (34). The (S)-acetolactate undergoes decarboxylation either spontaneously or by the enzyme acetolactate decarboxylase (E.C. 4.1.1.5) to the final by-product, UU-acetoin (35), which is meta-bolically inert. This process, for example, can be used for the production of both l- and d-2-aminobutyrate (36 and 37, respectively) (Scheme 19.21).8132 136 137... 

The presence of the second active form of MIPS with a —65 kDa subunit indicated that the inositol requirement of the organism might be provided by the interplay of two different MIPS enzymes, probably by differential expression through time and space. The results indicate that the —65 kDa MIPS protein of Synechocystis might be coded by the ORF sill981, annotated as a putative acetolactate synthase (unpublished data from this laboratory). This gene also functionally complements the inositol auxotrophic yeast strain FY250 and Schizosaccharomyces pombe, a natural inositol auxotroph, and the expressed protein is immunoreactive to anti MIPS antibody. 

The sulfonylureas, an extremely potent class of herbicides, act by inhibiting acetolactate synthase (ALS), which is the first common enzyme in the biosynthetic pathways leading to the branched chain amino acids. Two other unrelated classes of herbicides also act by interfering with this enzyme. We have cloned and characterized the genes encoding ALS from several higher plants. The ALS genes isolated from herbicide sensitive and herbicide resistant plants have been compared, and several mutations which confer the herbicide resistant phenotype have been identified. 

Acetolactate synthase (ALS) is the target enzyme for three unrelated classes of herbicides, the sulfonylureas, the imidazolinones, and the triazolopyrimidines. We have cloned the genes which specify acetolactate synthase from a variety of wild type plants, as well as from plants which are resistant to these herbicides. The molecular basis of herbicide resistance in these plants has been deduced by comparing the nucleotide sequences of the cloned sensitive and resistant ALS genes. By further comparing these sequences to ALS sequences obtained from herbicide-resistant yeast mutants, two patterns have become clear. First, the ALS sequences that can be mutated to cause resistance are in domains that are conserved between plants, yeast and bacteria. Second, identical molecular substitutions in ALS can confer herbicide resistance in both yeast and plants. 

In coll and typhlmurlum the structural genes for acetolactate synthase Isozymes have been Isolated (21,22,23 see Table III). The... 

Isolation of Other Structural Genes for Acetolactate Synthase... 

Figure 5.1 Production pathways of selected products discussed in the text. Gene/protein symbols aroF, DAMP synthase pykF, pyruvate kinase IdhA, lactate dehydrogenase alaA, alanine transaminase ilvIH, acetolactate synthase (a/sS = heterologous enzyme...

Figure 5.2 Isobutanol production via vaiine pathway and 1-butanol production via CoA-dependent pathway implemented. Common enzyme abbreviations or gene symbols ilvIH, acetolactate synthase ( . coli) aIsS, aceto-lactate synthase (Bacillus subtilis) ilvC, ace-tohydroxy acid isomeroreductase ( . coli) ilvD, dihydroxy acid dehydratase ( . coli) kivd, ketoisovalerate decarboxylase (Lactoccus...

Saika H, Horita J, Taguchi-Shiobara F, Nonaka S, Ayako NY, Iwakami S, Hori K, Matsumoto T, Tanaka T, Itoh T, Yano M, Kaku K, Shimizu T, Toki S (2014) A novel rice cytochrome P450 gene, CY-P72A31, confers tolerance to acetolactate synthase-inhibiting herbicides in rice and Arabidopsis. Plant Physiol 156 1232-1240... 

Three enzymes are involved in the synthesis of 2,3-BD a-acetolactate synthase (EC 4.1.3.18), a-acetolactate decarboxylase (EC 4.1.1.5), and butanediol dehydrogenase (also known as diacetyl [acetoin] reductase Larsen and Stormer 1973 Johansen et al. 1975 Stormer 1975). Two different enzymes form acetolactate from pyruvate. The first, termed catabolic a-acetolactate synthase, has a pH optimum of 5.8 in acetate and is part of the butanediol pathway. The other enzyme, termed anabolic a-acetolactate synthase or acetohydroxyacid synthetase, has been well studied and characterized and will not be discussed here. This enzyme is part of the biosynthetic pathway for isoleucine, leucine, and valine and is coded for by the ilvBN, ilvGM, and ilvH genes in E. colt and Salmonella typhimurium (Bryn and Stormer 1976). 

Although only limited results are currently available, enzymes associated with amino acid biosynthesis in higher plants appear to be nuclear encoded. Consequently, transport into chloroplasts would be expected to be facilitated by the presence of an N-terminal transit peptide on the initial translation product. This appears to be the case with acetolactate synthase (19), which is nuclear encoded and localized in chloroplasts (Chaleff and Ray, 1984). Evidence for nucleotide sequences that could code for an N-terminal transit peptide composed of between 85 and 99 residues was obtained for the genes isolated from Arabidopsis and Nicotiana (Mazur et al, 1987). The absence of synthesis of iS-adenosylmethionine in plastids is further supported by the apparent lack of a nucleotide sequence coding for a transit peptide in an adenylatetransferase Arabidopsis gene (Peleman et al., 1989). 

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