Abstract
An enzymatic preparation containing cysteine phytoproteases belonging to the papain family and isolated from the latex of Araujia hortorum Fourn. ( Asclepiadaceae) fruits was used as catalyst of the synthesis of the bitter dipeptide precursor Z-Ala-Phe-OMe in aqueous–organic media. Considering the good stability and activity of araujiain in different media, N, N-dimethylformamide (with low water content) and mixtures of the Tris–HCl buffer (0.1 M, pH 8.5) and hexane, ethyl acetate or propanone in 50:50 ratio were selected to perform the synthesis of that peptide. The araujiain-catalyzed synthesis was carried out at 40 °C using 2-mercaptoethanol as activator, TEA as neutralizing agent of the amino component (Phe-OMe·HCl) and different carboxylic components (Z-Ala, Z-Ala-OMe and Z-Ala- pNo). Under these conditions, araujiain only was able to form peptide bonds in biphasic media. The highest dipeptide conversion was obtained in the kinetically controlled synthesis using p-nitrophenyl ester derivative as carboxylic component in 50% (v/v) ethyl acetate. It is noteworthy that araujiain was unable to form oligopeptides derivatives, showing a good selectivity towards the synthesis of Z-Ala-Phe-OMe. For this reason and in general terms, araujiain constituted a new catalyst for the synthesis of small peptides.
Published Version
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