- Identification of 2, 3-dihydrodipicolinate as the product of the dihydrodipicolinate synthase reaction from Escherichia coli
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Dihydrodipicolinate synthase (DHDPS) catalyzes the first step in the pathway for the biosynthesis of L-lysine in most bacteria and plants. The substrates for the enzyme are pyruvate and L-aspartate-β-semialdehyde (ASA). The product of the reaction was originally proposed to be 2,3-dihydrodipicolinate (DHDP), but has now generally been assumed to be (4S)-4-hydroxy-2,3,4,5-tetrahydro-(2S)-dipicolinate (HTPA). ASA is unstable at high pH and it is proposed that ASA reacts with itself. At high pH ASA also reacts with Tris buffer and both reactions are largely reversible at low pH. It is proposed that the basic un-protonated form of the amine of Tris or the α-amine of ASA reacts with the aldehyde functional group of ASA to generate an imine product. Proton NMR spectra of ASA done at different pH values shows new NMR peaks at high pH, but not at low pH, confirming the presence of reaction products for ASA at high pH. The enzymatic product of the DHDPS reaction was examined at low pH by proton NMR starting with either 3 h-pyruvate or 3 d-pyruvate and identical NMR spectra were obtained with four new NMR peaks observed at 1.5, 2.3, 3.9 and 4.1 ppm in both cases. The NMR results were most consistent with DHDP as the reaction product. The UV-spectral studies of the DHDPS reaction shows the formation of an initial product with a broad spectral peak at 254 nM. The DHDPS reaction product was further examined by reduction of the enzymatic reaction components with borohydride followed by GC-MS analysis of the mixture. Three peaks were found at 88, 119 and 169 m/z, consistent with pyruvate, homoserine (reduction product of ASA), and the reduction product of DHDP (1,2,3,6-tetrahydropyridine-2,6-dicarboxylate). There was no indication for a peak associated with the reduced form of HTPA.
- Karsten, William E.,Nimmo, Susan A.,Liu, Jianguo,Chooback, Lilian
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- Biological evaluation of small molecule inhibitors of Mtb-ASADH enzyme
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In our previous work, some promising hits for Mtb-ASADH were identified using pharmacoinformatics approaches. Total ten compounds were selected for biological evaluation against Mtb-ASADH, nine of these were selected from virtual screening employing shape based and pharmacophore models and remaining one was designed from analog design. Cysteine has been reported as a covalently bonded inhibitor for Mtb-ASADH in a crystal structure (PDB ID: 3TZ6). Six out of ten compounds showed good inhibition of Mtb-ASADH. All these six molecules ZINC00108239, ZINC36358489, NSC4862, NSC109187, NSC51108, NSC226144 and S-carboxymethyl-L-cysteine showed IC50 values ranging from 65-100 μM. The binding mode analysis of S-carboxymethyl-L-cysteine, which showed highest inhibitory activity among tested compounds, exhibited binding interactions with catalytic residues Arg99, Arg249, Lys227 and His256. These studies can be further exploited for lead optimization and rational drug designing to find new leads against Tuberculosis.
- Kumar, Rajender,Sethi, Ratnika,Shah, Purvi,Roy, Ipsita,Singh, Inder Pal,Bharatam,Tewari, Rupinder,Garg, Prabha
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p. 587 - 590
(2016/07/29)
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- Synthesis of deuterium labelled L- and D-glutamate semialdehydes and their evaluation as substrates for carboxymethylproline synthase (CarB) - Implications for carbapenem biosynthesis
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Carboxymethylproline synthase was shown to condense L-glutamate semialdehyde with malonyl-coenzyme A to produce (2S,5S)-carboxymethylproline, while incubation of D-glutamate semialdehyde results only in uncoupled turnover of malonyl-CoA. The Royal Society of Chemistry 2005.
- Sorensen, John L.,Sleeman, Mark C.,Schofield, Christopher J.
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p. 1155 - 1157
(2007/10/03)
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- Vinylogous amide analogues of diaminopimelic acid (DAP) as inhibitors of enzymes involved in bacterial lysine biosynthesis.
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[reaction: see text] Vinylogous amides 5 and 6 have been synthesized from L-propargyl glycine and tested against diaminopimelate (DAP) enzymes involved in bacterial lysine biosynthesis. Both are reversible inhibitors of DAP D-dehydrogenase and DAP epimerase with IC(50) values in the 500 microM range. Compound 5 shows competitive inhibition against the L-dihydrodipicolinate (DHDP) reductase with a K(i) value of 32 microM, which is comparable to the planar dipicolinate 16 (K(i) = 26 microM), the best known inhibitor of the enzyme.
- Caplan,Zheng,Blanchard,Vederas
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p. 3857 - 3860
(2007/10/03)
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- Under-flame Reaction of Sulfur-containing Amino Acids by a Hydrogen-Oxygen Flame
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Methionine was subjected to a flame-induced reaction in water or in an aqueous formic acid solution by using a hydrogen (50%)-oxygen (50%), hydrogen (87%)-oxygen (13%) and hydrogen diffusion flame. Besides the already-known stepwise oxidation by a hydroxyl radical, the contribution of a hydrogen atom from the flame to the reaction was recognized when the hydrogen-rich mixtures were employed. Homoserine was obtained under all the reaction conditions employed here, and glutamic acid when employing aqueous formic acid as a solvent. A common intermediate, the 3-carboxy-3-aminopropyl radical, appeared to exist in the reaction pathway. A coupling reaction of this radical with a hydrogen atom, hydroxyl radical and hydroxycarbonyl radical afforded 2-aminobutyric acid, homoserine and glutamic acid, respectively. Lanthionine and S-methylcysteine underwent the same reactions. Increasing the hydrogen content of the fuel and adding formic acid to the solvent resulted in retarding the reaction rate. The latter modification of the reaction system also brought about greater stability of the reaction products.
- Nomoto, Shinya,Shimoyama, Akira,Shiraishi, Susumu,Seno, Tomoyuki,Sahara, Denzo
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p. 643 - 649
(2007/10/03)
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- (S)-aspartate semi-aldehyde: Synthetic and structural studies
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We report a novel synthesis of (S)-aspartate semi-aldehyde, (S)-ASA, 1, a key intermediate in the biosynthesis of lysine, based on hydrolysis of an enol ether precursor, (S)-2-amino-4-methoxybut-3-enoic acid, 10, (S)-ASA is conveniently and quantitatively liberated from this stable intermediate and can be used in biological studies directly, since methanol is the only side-product. Enzyme inhibition studies and chemical precedent imply a cyclic lactol structure might be significant; heteronuclear multibond coupling (HMBC) measurements, however, are consistent with the hydrate being the predominant species in aqueous solution.
- Coulter, Carolyn V.,Gerrard, Juliet A.,Kraunsoe, James A. E.,Moore, Deborah J.,Pratt, Andrew J.
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p. 7127 - 7136
(2007/10/03)
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