- Epimerization of cyclic alanyl-alanine in basic solutions
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Alanine anhydrides (Cyclo-(Ala-Ala)) are the simplest dipeptides that have two chiral centers and three diastereomers: Cyclo-(L-Ala-L-Ala), Cyclo-(D-Ala-D-Ala), and Cyclo-(L-Ala-D-Ala). Analysis of the epimerization of these peptides may throw light on the development of homochirality in proteins. We show that the epimerization rate of Cyclo-(L-Ala-L-Ala) and Cyclo-(D-Ala-D-Ala) is higher than that of Cyclo-(L-Ala-D-Ala), while the ring-opening rates of Cyclo-(L-Ala-L-Ala) and Cyclo-(D-Ala-D-Ala) arelower than that of Cyclo-(L-Ala-D-Ala) in basic aqueous solutions. The total reaction resulted in the preferred stability of Cyclo-(L-Ala-L-Ala) and Cyclo-(D-Ala-D-Ala) to Cyclo-(D-Ala-L-Ala).
- Munegumi, Toratane,Fujimoto, Takeshi,Michiotakada,Nozominagashima
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- Aminolytic reaction catalyzed by d-stereospecific amidohydrolases from Streptomyces spp
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From investigation of 2000 soil isolates, we identified two serine-type amidohydrolases that can hydrolyze d-aminoacyl derivatives from the culture supernatant of Streptomyces species 82F2 and 83D12. The enzymes, redesignated as 82F2-DAP and 83D12-DAP, were purified for homogeneity and characterized. Each enzyme had molecular mass of approximately 40 kDa, and each showed moderate stability with respect to temperature and pH. Among hydrolytic activities toward d-aminoacyl-pNAs, the enzymes showed strict specificity toward d-Phe-pNA, but showed broad specificity toward d-aminoacyl esters. The specific activity for d-Phe-pNA hydrolysis of 82F2-DAP was ten-fold higher than that of 83D12-DAP. As a second function, each enzyme showed peptide bond formation activity by its function of aminolysis reaction. Based on results of d-Phe-d-Phe synthesis under various conditions, we propose a reaction mechanism for d-Phe-d-Phe production. Furthermore, the enzymes exhibited peptide elongation activity, producing oligo homopeptide in a one-pot reaction. We cloned the genes encoding each enzyme, which revealed that the primary structure of each enzyme showed 30-60% identity with those of peptidases belonging to the clan SE, S12 peptidase family categorized as serine peptidase with d-stereospecificity.
- Arima, Jiro,Ito, Hitomi,Hatanaka, Tadashi,Mori, Nobuhiro
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experimental part
p. 1460 - 1469
(2012/01/12)
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- Stereoselective Alkylation of Glycine Units in Dipeptide Derivatives: "Chirality Transfer" via a Pivalaldehyde N,N-Acetal Center
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Dipeptide esters (of glycylglycine, glycylalanine, alanylglycine) and aldehydes (isobutyraldehyde, pivalaldehyde, benzaldehyde) are condensed to (4-oxoimidazolidin-3-yl)acetates and -propionates (1-3).Lithium enolates of these derivatives, are generated (
- Polt, Robin,Seebach, Dieter
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p. 2622 - 2632
(2007/10/02)
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- 178. Alkylation of Imidazolidinone Dipeptide Derivatives: Preparation of Enantiomerically Pure Di- and Tripeptides by "Chirality Transfer" via a Pivalaldehyde N,N-Acetal Center
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Glycylglycine, glycyl-(S)-alanine, and (S)-alanylglycine esters are cyclized through pivalaldehyde imines to give dipeptide-derived 3-(benzyloxycarbonyl)-2-(tert-butyl)-5-oxoimidazolidine-1-acetates 1-3.These are alkylated diastereoselecively by Li-enolat
- Polt, Robin,Seebach, Dieter
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p. 1930 - 1936
(2007/10/02)
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