Even-numbered peptides from a papain hydrolysate of silk fibroin

초록

A protease with broad substrate specificity usually produces a complex peptide mixture. However, even-numbered peptides were obtained at high proportion upon papain hydrolysis of fibroin composed of highly repetitive Ala- and Gly-rich blocks. MALDI-TOF and ESI mass spectrometric analysis revealed that the even-numbered peptides were in the forms of di-, tetra-, hexa-, and octa-peptides with repeating units in combination of Ala-Gly, Ser-Gly, Tyr-Gly, and Val-Gly. Application of tandem mass spectrometry identified the sequences of the tetra-peptides to be in the order of Ala-Gly-X-Gly (X = Tyr or Val). Therefore, the substrate specificity of papain and the unique repetitive sequence of fibroin generated the hydrolysate composed of even number of amino acids at a high percentage. In this work, fibroin hydrolysate was investigated as an example of an end product of protein hydrolysis, which provides a clue to understand the fate of peptides in a protein hydrolysate. (C) 2010 Elsevier B.V. All rights reserved.

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