A novel ornithine-containing tripeptide isolated from the extract of the brackish-water bivalve Corbicula japonica.

Abstract Previous studies have demonstrated that frozen preparations of the brackish-water bivalve Corbicula japonica significantly increase the content of free ornithine found in its extracts. Here we report a novel ornithine-containing tripeptide commonly found in C. japonica , which is believed to be the source of increased free ornithine. The new peptide, named acorbine, was isolated from extracts of this bivalve obtained using ultra-filtration and gel permeation chromatography. Acorbine is comprised of N 2 -[ N 2 -(β-alanyl)- l -ornithyl]- l -ornithine as determined by amino acid composition analysis, N- and C-terminal amino acid analyses, proton nuclear magnetic resonance spectrometry, and chirality analysis of the ornithine residue. The total amount of β-alanine and ornithine in the extract remained constant regardless of the temperature at which the bivalve was processed. The amount of free β-alanine and ornithine increased significantly when the bivalve was frozen, with a corresponding decrease in peptidic β-alanine and ornithine. The results suggest that changing the growth conditions triggers tripeptide proteolysis within the bivalve, which ultimately manifests in increased free β-alanine and ornithine.