- Benzimidazole analogs of l-tryptophan are substrates and inhibitors of tryptophan indole lyase from Escherichia coli
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Tryptophan indole lyase (TIL), an enzyme found in Escherichia coli and related enterobacteria, produces indole from l-tryptophan (l-Trp). Indole is a signaling molecule in bacteria, affecting biofilm formation, pathogenicity and antibiotic resistance. β-(Benzimidazol-1-yl)-l-alanine (BZI-Ala), 2-amino-4-(benzimidazol-1-yl)butyric acid (homo-BZI-Ala) and 2-amino-5-(benzimidazol-1-yl)pentanoic acid (bishomo-BZI-Ala) were synthesized and tested as substrates and inhibitors of TIL. BZI-Ala is a good substrate of TIL, with Km = 300 μm, kcat = 5.6 s-1 and kcat/Km = 1.9 × 104, similar to l-Trp. BZI-Ala is also a good substrate for H463F mutant TIL, which has very low activity with l-Trp. In contrast, homo-BZI-Ala was found to be a potent competitive inhibitor of TIL, with a Ki of 13.4 μm. However, the higher homolog, bishomo-BZI-Ala, was inactive as an inhibitor of TIL at a concentration of 600 μm, and is thus a much weaker inhibitor. The reaction of TIL with BZI-Ala was too fast to be observed in the stopped-flow spectrophotometer, and shows an aldimine intermediate in the steady state. However, H463F TIL shows equilibrating mixtures of aldimine and quinonoid complexes in the steady state. The spectra of the reaction of TIL with homo-BZI-Ala show a rapidly formed intermediate absorbing at 340 nm, probably a gem-diamine, that decays slowly to form a quinonoid complex absorbing at 494 nm. The potent binding of homo-BZI-Ala may be due to it being a 'bi-product' analog of the indole-α-aminoacrylate complex. These results demonstrate that an amino acid substrate may be converted to a potent inhibitor of TIL simply by homologation, which may be useful in the design of other potent TIL inhibitors. β-(Benzimidazol-1-yl)-l-alanine (BZI-Ala), 2-amino-4-(benzimidazol-1-yl) butyric acid (homo-BZI-Ala), and 2-amino-5-(benzimidazol-1-yl)pentanoic acid (bishomo-BZI-Ala) were synthesized and tested as substrates and inhibitors of tryptophan indole-lyase (TIL), an enzyme found in Escherichia coli and related enterobacteria. BZI-Ala is a good substrate of TIL, homo-BZI-Ala is a potent competitive inhibitor of TIL, with Ki of 13.4 μM, but bishomo-BZI-Ala, was inactive as an inhibitor of TIL. 2013 The Authors Journal compilation
- Harris, Austin P.,Phillips, Robert S.
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p. 1807 - 1817
(2013/06/05)
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- Improved efficiency and selectivity in peptide synthesis: Use of triethylsilane as a carbocation scavenger in deprotection of t-butyl esters and t-butoxycarbonyl-protected sites
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The use of triethylsilane as a carbocation scavenger in the presence of trifluoroacetic acid in dichloromethane leads to increased yields, decreased reaction times, simple work-up and improved selectivity for the deprotection of t-butyl ester and t-butoxycarbonyl sites in protected amino-acids and peptides in the presence of other acid-sensitive protecting groups such as the benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, O- and S-benzyl and t-butylthio groups.
- Mehta, Anita,Jaouhari, Rabih,Benson, Timothy J.,Douglas, Kenneth T.
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p. 5441 - 5444
(2007/10/02)
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- Multigram synthesis of N(G)-methyl-(L)-arginine and its analytical characterization
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A multigram preparation and analytical characterization of N(G)-methyl-(L)-arginine (L-NMMA) 1, the most important inhibitor of the biosynthesis of Endothelium-Derived Relaxing Factor (EDRF), is reported.
- Ferrario,Levi,Sala,Trupiano
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- An alternative synthesis of N5-Acetyl-N5-hydroxy-L-ornithine from L-Ornithine
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N5-Acetyl-N5-hydroxy-L-ornithine is obtained from L-ornithine in 20% overall yield via oxidation of the ω-amino group in N2-benzyloxycarbonyl-L-ornithine tert-butyl ester with dibenzoyl peroxide and subsequent N5-acetylation.
- Milewska,Chimiak
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p. 233 - 234
(2007/10/02)
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