Rapid Germination of Sulfonylurea-ResistantKochia scopariaL. Accessions is Associated with Elevated Seed Levels of Branched Chain Amino Acids

Weed Science ◽  
1993 ◽  
Vol 41 (1) ◽  
pp. 18-22 ◽  
Author(s):  
William E. Dyer ◽  
Peng W. Chee ◽  
Peter K. Fay
Keyword(s):  
Amino Acids ◽  
Thermal Gradient ◽  
Feedback Inhibition ◽  
Acetolactate Synthase ◽  
Branched Chain Amino Acids ◽  
Resistant Accession ◽  
Early Germination ◽  
Percent Germination ◽  
Soil Temperatures ◽  
Branched Chain

Field observations indicate that sulfonylurea-resistant kochia may germinate at lower soil temperatures and/or germinate more rapidly than susceptible kochia in the absence of herbicide. To investigate this possibility, seeds from three resistant and two susceptible kochia accessions were germinated at temperatures ranging from 4.6 to 13.2 C on thermal gradient plates. At 4.6 and 13.2 C, germination rates of all resistant accessions were higher than susceptible accessions, while germination rates of one resistant accession were higher than susceptible accessions at 7.2 and 10.5 C. Percent germination of all resistant accessions was significantly higher than susceptible accessions after 48 h at 4.6 C. At higher temperatures, percent germination of some resistant accessions was higher after 12 or 24 h, but germination of all accessions was similar at later times. HPLC analysis revealed that seeds from resistant accessions contained about 2-fold higher free levels of branched chain amino acids than seeds from susceptible accessions. The results indicate that mutations conferring resistance to sulfonylurea herbicides in these kochia accessions may concomitantly reduce or abolish acetolactate synthase sensitivity to normal feedback inhibition patterns, resulting in elevated levels of branched chain amino acids available for cell division and growth during early germination.

Fun with Mutants: Applying Genetic Methods to Problems of Weed Physiology

Weed Science ◽  
1991 ◽  
Vol 39 (3) ◽  
pp. 489-496 ◽  
Author(s):  
Michael L. Christianson
Keyword(s):  
Amino Acids ◽  
Case History ◽  
Potential Problem ◽  
Plant Cells ◽  
Acetolactate Synthase ◽  
Branched Chain Amino Acids ◽  
Successful Development ◽  
Amino Butyric Acid ◽  
Branched Chain ◽  
Whole Plants

Genetics can be a powerful adjunct to just about any kind of physiological study, including weed physiology or weed/herbicide interactions. Making, mapping, and reverting mutations is simple and straightforward. Making mutants can be as simple as isolating variant individuals from the “wild”, as uncomplicated as doing seed mutagenesis in your laboratory, or as sneaky as recovering mutants as sectors in whole plants. The overall principles for successful development of a protocol for seed mutagenesis of weeds are described and potential problem areas noted. These generalities are illustrated with a specific case history, that of chlorsulfuron. Although chlorsulfuron is accurately described as an inhibitor of the synthesis of branched chain amino acids, careful physiological examination suggests that it kills plant cells, not by starvation for amino acids, but by active toxicity of a metabolite, α-amino butyric acid, produced from a precursor available for diversion in cells with inhibited acetolactate synthase (EC 4.1.3.18, ALS). The story of dominant resistance due to an altered ALS enzyme is well known; analysis using additional mutants fleshes out the story of how chlorsulfuron works. Such analysis has the potential to help unravel other problems in weed physiology.

scholarly journals Metabolic engineering of Corynebacterium glutamicum for producing branched chain amino acids

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Shengzhu Yu ◽  
Bo Zheng ◽  
Zhenya Chen ◽  
Yi-Xin Huo
Keyword(s):  
Amino Acids ◽  
Metabolic Engineering ◽  
Corynebacterium Glutamicum ◽  
Animal Feed ◽  
Feedback Inhibition ◽  
Value Added ◽  
Branched Chain Amino Acids ◽  
High Yield ◽  
Acetohydroxy Acid Synthase ◽  
Branched Chain

Abstract Background Branched chain amino acids (BCAAs) are widely applied in the food, pharmaceutical, and animal feed industries. Traditional chemical synthetic and enzymatic BCAAs production in vitro has been hampered by expensive raw materials, harsh reaction conditions, and environmental pollution. Microbial metabolic engineering has attracted considerable attention as an alternative method for BCAAs biosynthesis because it is environmentally friendly and delivers high yield. Main text Corynebacterium glutamicum (C. glutamicum) possesses clear genetic background and mature gene manipulation toolbox, and has been utilized as industrial host for producing BCAAs. Acetohydroxy acid synthase (AHAS) is a crucial enzyme in the BCAAs biosynthetic pathway of C. glutamicum, but feedback inhibition is a disadvantage. We therefore reviewed AHAS modifications that relieve feedback inhibition and then investigated the importance of AHAS modifications in regulating production ratios of three BCAAs. We have comprehensively summarized and discussed metabolic engineering strategies to promote BCAAs synthesis in C. glutamicum and offer solutions to the barriers associated with BCAAs biosynthesis. We also considered the future applications of strains that could produce abundant amounts of BCAAs. Conclusions Branched chain amino acids have been synthesized by engineering the metabolism of C. glutamicum. Future investigations should focus on the feedback inhibition and/or transcription attenuation mechanisms of crucial enzymes. Enzymes with substrate specificity should be developed and applied to the production of individual BCAAs. The strategies used to construct strains producing BCAAs provide guidance for the biosynthesis of other high value-added compounds.

Biosynthesis of Branched-Chain Amino Acids in Schizosaccharomyces pombe: Regulation of the Enzymes Involved in Isoleucine, Valine, and Leucine Synthesis

1974 ◽  
Vol 52 (1) ◽  
pp. 51-59 ◽  
Author(s):  
Roderick A. McDonald ◽  
T. Satyanarayana ◽  
J. G. Kaplan
Keyword(s):  
Amino Acids ◽  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Feedback Inhibition ◽  
Branched Chain Amino Acids ◽  
Baker’S Yeast ◽  
Baker's Yeast ◽  
Threonine Deaminase ◽  
Branched Chain ◽  
Ph Range

The activities and regulation of the enzymes of the synthetic pathway of branched-chain amino acids were investigated in the fission yeast, Schizosaccharomyces pombe. Previous studies had shown the presence of threonine deaminase (TD) and acetohydroxy acid synthetase (AHAS). The remaining isoleucine–valine enzymes, isomeroreductase (IR), dehydrase, and transaminase B, have now been characterized in cell-free extracts, indicating the presence in this yeast of the complete pathway as demonstrated in other microorganisms. α-Isopropylmalate synthetase (IPMS), the first enzyme of the leucine pathway, has properties of a typical regulatory enzyme; it is most active in the pH range 7.5–8.5, but is most sensitive to feedback inhibition by L-leucine at pH 6.5–7.0. Unlike the situation in baker's yeast, only AHAS and IR appeared to be subject to multivalent repression. TD was relatively resistant to any change in level, and AHAS was repressible by valine included in the growth medium. IPMS was repressed when cells were grown in complex medium; leucine alone did not cause repression, and in contrast with baker's yeast, neither did leucine plus threonine or a combination of all three branched-chain amino acids.

Heterologous Expression and Functional Characterization of Catalytic Subunit of Rice Acetohydroxyacid Synthase

2019 ◽  
Vol 26 (3) ◽  
pp. 176-183
Author(s):  
Ghazaleh Arabzadeh ◽  
Azar Shahpiri
Keyword(s):  
Amino Acids ◽  
Specific Activity ◽  
Feedback Inhibition ◽  
Functional Characterization ◽  
Branched Chain Amino Acids ◽  
Biochemical Properties ◽  
Catalytic Subunit ◽  
Acetohydroxyacid Synthase ◽  
Branched Chain

Background: Acetohydroxyacid Synthase (AHAS) is the first enzyme in the biosynthesis pathway of the branched chain amino acids. AHAS is the common target site of five herbicide chemical groups: sulfonylurea, imidazolinone, triazolopyrimidine, pyrimidinyl-thiobenzoates, and sulfonyl-aminocarbonyl-triazolinone. </P><P> Objective: The purification of protein enabled us to study the physical and biochemical properties of the enzyme. In addition in vitro activity of this enzyme was tested in the presence of four different sulfonylureaherbicides and the feedback regulation of enzyme was analyzed in the presence of branched amino acids. Methods: The gene encoding catalytic subunit of rice AHAS (cOsAHAS) without part of the chloroplast transit sequence was cloned into the bacterial expression vector pET41a and heterologously expressed in Escherichia coli as carboxy-terminal extensions of glutathione-S-transferase (GST).The soluble protein was purified using affinity chromatography. The measurement of GSTOsAHAS activity was performed under optimized conditions at present of branched-chain amino acids and sulfonylurea herbicides independently. Results: The optimum pH and temperature for GST-cOsAHAS activity was 8.0 and 37 °C, respectively. The specific activity and Km value of this enzyme toward pyruvate were 0.08 U/mg and 30 mM, respectively.GST-cOsAHAS was inhibited by herbicides tribenuron, sulfosulfuron, nicosulfuron and bensulfuron while the enzyme was insensitivieto end products. Conclusion: These results suggest that the recombinant form of GST-cOsAHAS is functionally active and carries the binding site for sulfynylurea herbicides. Furthermore, GST-cOsAHAS was insensitive to feedback inhibition by endproducts which indicates the existence of a regulator subunit in rice AHAS as previously has been described in other plant AHASs.

Two Forms of Herbicide-Sensitive Acetolactate Synthase under Different Control by 2-Oxobutyrate in Rhodospivillum rubrum

1990 ◽  
Vol 45 (9-10) ◽  
pp. 999-1003
Author(s):  
Jobst-Heinrich Klemme ◽  
Irmgard Schneider
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Rhodospirillum Rubrum ◽  
Culture Media ◽  
Acetolactate Synthase ◽  
Branched Chain Amino Acids ◽  
Standard Test ◽  
Lag Phase ◽  
Test Mixture ◽  
Branched Chain

Regulation of acetolactate synthase (ALS, EC 4.1.3.18) in the phototrophic prokaryote Rhodospirillum rubrum was studied. In cell free extracts of 5 strains investigated, enzyme activity was very labile (about 80% loss of activity within 12h during storage at 4 °C) but was stabilized to some extent by 10 (μM FAD and 20 vol.% glycerol. By filtration of extracts through Superose 6 HR gels (FPLC technique), ALS activity of all strains was separated in two fractions of 200 and 600 kDa, respectively. The enzyme fractions had about the same affinity to pyruvate (ATm = 1.6 - 1.8 m M) , the same sensitivity to L-valine (50 and 65% inhibition by 0.1 m M valine in the standard test mixture) and the herbicide sulfometuron methyl (90 and 92% inhibition by 1 μM herbicide), but differed greatly in their sensitivity to inhibition by 0.4 m NaCl. In culture media with 2-oxobutyrate (2-OB), growth began only after a lag-phase of several days (5 days with 1 mM of the inhibitor). Cells grown in the presence of 2-OB had a reduced total ALS activity and did not contain the 200 kDa fraction. The inhibition of ALS by valine was noncompetitive in respect to pyruvate (K1= 0.l m M ) . From other branched-chain amino acids tested (L-leucine, L-isoleucine, norvaline, norleucine) only isoleucine was inhibitory (K1; = 3.1 m M )

Rapid Diagnosis of Als/Ahas-Resistant Weeds

1993 ◽  
Vol 7 (2) ◽  
pp. 519-524 ◽  
Author(s):  
B. Clifford Gerwick ◽  
Linda C. Mireles ◽  
Robert J. Eilers
Keyword(s):  
Amino Acids ◽  
Acetolactate Synthase ◽  
Branched Chain Amino Acids ◽  
Rapid Diagnosis ◽  
Acetohydroxyacid Synthase ◽  
Number Of Species ◽  
Apical Leaf ◽  
Diagnosis Method ◽  
Branched Chain ◽  
Leaf Disks

A method to rapidly identify acetolactate synthase/acetohydroxyacid synthase (ALS/AHAS)-resistant weeds is described based upon the differential accumulation of acetoin in the presence and absence of an ALS/AHAS inhibitor herbicide. Acetoin accumulation is induced by inhibition of ketol-acid reductoisomerase (KARI), the enzyme immediately following ALS/AHAS in the biosynthesis of branched-chain amino acids. Inhibition of ALS/AHAS prevents the build up of acetoin and forms the basis for distinguishing between sensitive and resistant biotypes. A new inhibitor of KARI, 1,1-cyclopropanedicarboxylic acid (CPCA), is described and was found to cause acetoin accumulation in velvetleaf leaf disks over the concentration range of 2 to 100 000 μM. In the presence of CPCA, a number of species important to monitor for ALS/AHAS resistance were found to accumulate acetoin at rates sufficient for resistance diagnosis in 2 to 8 h. In velvetleaf, the youngest apical leaf was found to be the most active in acetoin accumulation. The resistance diagnosis method was validated by clearly distinguishing between imazaquin-sensitive and imazaquin-resistant cocklebur biotypes.

The Weight Loss Effects of Branched Chain Amino Acids and Vitamin B6: A Randomized Controlled Trial on Obese and Overweight Women

2018 ◽  
Vol 88 (1-2) ◽  
pp. 80-89 ◽  
Author(s):  
Zahra Shakibay Novin ◽  
Saeed Ghavamzadeh ◽  
Alireza Mehdizadeh
Keyword(s):  
Amino Acids ◽  
Weight Loss ◽  
Body Composition ◽  
Vitamin B6 ◽  
Controlled Trial ◽  
Density Lipoprotein ◽  
Branched Chain Amino Acids ◽  
Model Assessment ◽  
Waist To Hip Ratio ◽  
Branched Chain

Abstract. Branched chain amino acids (BCAA), with vitamin B6 have been reported to improve fat metabolism and muscle synthesis. We hypothesized that supplementation with BCAA and vitamin B6 would result in more weight loss and improve body composition and blood markers related to cardiovascular diseases. Our aim was to determine whether the mentioned supplementation would affect weight loss, body composition, and cardiovascular risk factors during weight loss intervention. To this end, we performed a placebo-controlled randomized clinical trial in 42 overweight and obese women (BMI = 25–34.9 kg/m2). Taking a four-week moderate deficit calorie diet (–500 kcal/day), participants were randomized to receive BCAA (6 g/day) with vitamin B6 (40 mg/day) or placebo. Body composition variables measured with the use of bioelectrical impedance analysis, homeostatic model assessment, and plasma insulin, Low density lipoprotein, High density lipoprotein, Total Cholesterol, Triglyceride, and fasting blood sugar were measured. The result indicated that, weight loss was not significantly affected by BCAA and vitamin B6 supplementation (–2.43 ± 1.02 kg) or placebo (–1.64 ± 1.48 kg). However, significant time × treatment interactions in waist to hip ratio (P = 0.005), left leg lean (P = 0.004) and right leg lean (P = 0.023) were observed. Overall, supplementation with BCAA and vitamin B6 could preserve legs lean and also attenuated waist to hip ratio.

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