Synthesis of Modified Aldonic Acids and Studies of Their Substrate Efficiency for Dihydroxy Acid Dehydratase (DHAD)

1996 ◽  
Vol 49 (3) ◽  
pp. 349 ◽  
Author(s):  
G Limberg ◽  
G Limberg ◽  
J Thiem ◽  
J Thiem
Keyword(s):  
Active Site ◽  
Biosynthetic Pathway ◽  
Branched Chain Amino Acids ◽  
Artificial Substrates ◽  
The Novel ◽  
Enzymatic Conversion ◽  
Preparative Scale ◽  
Dihydroxy Acid ◽  
Acid Dehydratase ◽  
Branched Chain

Modified aldopentonic and aldohexonic acids were synthesized in order to study the electronic requirements for a successful enzymatic conversion into their corresponding 2-keto 3-deoxy analogues by dihydroxy acid dehydratase (DHAD), an enzyme from the biosynthetic pathway of branched chain amino acids. Analytical tests with the novel artificial substrates (18)-(21) and (27) provided evidence that the amount of conversion could be enhanced by replacement of the hydroxy group at C4 of L-arabinonic acid (21) with less electron-withdrawing, ambivalent or electron-donating substituents. Modified aldohexonic acids were no substrates for DHAD, perhaps due to less perfect binding to the active site presumably for steric reasons. For 4-deoxy-L-threo-pentonic acid (18) the enzymatic conversion into 3,4-dideoxy-2-ketopentonic acid (29) by DHAD could be achieved on a preparative scale.

Acetohydroxyacid synthase and its role in the biosynthetic pathway for branched-chain amino acids

Amino Acids ◽  
2006 ◽  
Vol 31 (2) ◽  
pp. 173-210 ◽  
Author(s):  
J. A. McCourt ◽  
R. G. Duggleby
Keyword(s):  
Amino Acids ◽  
Biosynthetic Pathway ◽  
Branched Chain Amino Acids ◽  
Acetohydroxyacid Synthase ◽  
Branched Chain

Studies on the Active Site of Dihydroxy-acid Dehydratase

1993 ◽  
Vol 21 (4) ◽  
pp. 367-385 ◽  
Author(s):  
D.H. Flint ◽  
A. Nudelman
Keyword(s):  
Active Site ◽  
Dihydroxy Acid ◽  
Acid Dehydratase

scholarly journals Purification and characterization of Ak.1 protease, a thermostable subtilisin with a disulphide bond in the substrate-binding cleft

2000 ◽  
Vol 350 (1) ◽  
pp. 321-328 ◽  
Author(s):  
Helen S. TOOGOOD ◽  
Clyde A. SMITH ◽  
Edward N. BAKER ◽  
Roy M. DANIEL
Keyword(s):  
Active Site ◽  
Substrate Binding ◽  
Fold Increase ◽  
Branched Chain Amino Acids ◽  
Disulphide Bond ◽  
Purification And Characterization ◽  
Active Site Cleft ◽  
Binding Cleft ◽  
Branched Chain

Ak.1 protease, a thermostable subtilisin isolated originally from Bacillus st. Ak.1, was purified to homogeneity from the Escherichia coli clone PB5517. It is active against substrates containing neutral or hydrophobic branched-chain amino acids at the P1 site, such as valine, alanine or phenylalanine. The Km and kcat of the enzyme decrease with decreasing temperature, though not to the same degree with all substrates, suggesting that specificity changes with temperature. The protease is markedly stabilized by Ca2+ ions. At 70°C, a 10-fold increase in Ca2+ concentration increases the half-life by three orders of magnitude. Ak.1 protease is stabilized by Ca2+ to a greater extent than is thermitase. This may be due, in part, to the presence of an extra Ca2+-binding site in Ak.1 protease. Other metal ions, such as Sr2+, increase the thermostability of the enzyme, but to a significantly lower degree than does Ca2+. The structure of the protease showed the presence of a disulphide bond located within the active-site cleft. This bond influences both enzyme activity and thermostability. The disulphide bond appears to have a dual role: maintaining the integrity of the substrate-binding cleft and increasing the thermostability of the protease. The protease was originally investigated to determine its usefulness in the clean-up of DNA at high temperatures. However, it was found that this protease has a limited substrate specificity, so this application was not explored further.

Mechanism and Inhibitor Exploration with Binuclear Mg Ketol‐Acid Reductoisomerase: Targeting the Biosynthetic Pathway of Branched‐Chain Amino Acids

ChemBioChem ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 381-391
Author(s):  
Ming‐Jia Yu ◽  
Jue Wu ◽  
Shi‐Lu Chen
Keyword(s):  
Amino Acids ◽  
Biosynthetic Pathway ◽  
Branched Chain Amino Acids ◽  
Branched Chain

scholarly journals Structural Rearrangements of a Dodecameric Ketol-Acid Reductoisomerase Isolated from a Marine Thermophilic Methanogen

Biomolecules ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1679
Author(s):  
Olivier Nicolas Lemaire ◽  
Marie-Caroline Müller ◽  
Jörg Kahnt ◽  
Tristan Wagner
Keyword(s):  
Amino Acids ◽  
Active Site ◽  
Methanogenic Archaea ◽  
Branched Chain Amino Acids ◽  
Structural Rearrangements ◽  
Coenzyme Binding ◽  
High Conservation ◽  
Branched Chain ◽  
Very High

Ketol-acid reductoisomerase (KARI) orchestrates the biosynthesis of branched-chain amino acids, an elementary reaction in prototrophic organisms as well as a valuable process in biotechnology. Bacterial KARIs belonging to class I organise as dimers or dodecamers and were intensively studied to understand their remarkable specificity towards NADH or NADPH, but also to develop antibiotics. Here, we present the first structural study on a KARI natively isolated from a methanogenic archaea. The dodecameric structure of 0.44-MDa was obtained in two different conformations, an open and close state refined to a resolution of 2.2-Å and 2.1-Å, respectively. These structures illustrate the conformational movement required for substrate and coenzyme binding. While the close state presents the complete NADP bound in front of a partially occupied Mg2+-site, the Mg2+-free open state contains a tartrate at the nicotinamide location and a bound NADP with the adenine-nicotinamide protruding out of the active site. Structural comparisons show a very high conservation of the active site environment and detailed analyses point towards few specific residues required for the dodecamerisation. These residues are not conserved in other dodecameric KARIs that stabilise their trimeric interface differently, suggesting that dodecamerisation, the cellular role of which is still unknown, might have occurred several times in the evolution of KARIs.

The chemical mechanisms of the enzymes in the branched-chain amino acids biosynthetic pathway and their applications

Biochimie ◽  
2021 ◽  
Vol 184 ◽  
pp. 72-87
Author(s):  
Yan-Fei Liang ◽  
Zi-Xian Long ◽  
Ya-Jian Zhang ◽  
Cai-Yun Luo ◽  
Le-Tian Yan ◽  
...  
Keyword(s):  
Amino Acids ◽  
Biosynthetic Pathway ◽  
Branched Chain Amino Acids ◽  
Chemical Mechanisms ◽  
Branched Chain

Only L-valine among branched-chain amino acids is effective in promoting the growth of the small intestinal mucosa

2001 ◽  
Vol 120 (5) ◽  
pp. A676-A676
Author(s):  
T TAKAHASHI ◽  
H DOI ◽  
H KOMATSU ◽  
K SATO ◽  
O UEDA ◽  
...  
Keyword(s):  
Amino Acids ◽  
Intestinal Mucosa ◽  
Branched Chain Amino Acids ◽  
Small Intestinal Mucosa ◽  
Small Intestinal ◽  
Branched Chain

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.

Branched chain amino acids decrease top-down event-related potentials in healthy subjects

2007 ◽  
Vol 40 (05) ◽  
Author(s):  
AH Neuhaus ◽  
TE Goldberg ◽  
Y Hassoun ◽  
JA Bates ◽  
KW Nassauer ◽  
...  
Keyword(s):  
Amino Acids ◽  
Healthy Subjects ◽  
Event Related Potentials ◽  
Branched Chain Amino Acids ◽  
Top Down ◽  
Related Potentials ◽  
Branched Chain
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