S. Si Ahmed Zennia, A. Mati, F. Saulnier, Y. Verdier, G. Chiappetta, G. Mulliert, L. Miclo, J. Vinh, J.M. Girardet
Food Chem. 187 307-315 (2015). DOI

Travail réalisé sur le site de l’ESPCI.

Abstract

Nonenzymatic deamidation of asparaginyl residues can occur spontaneously under physiological conditions principally when a glycyl residue is at the carboxyl side of Asn and leads to formation of aspartyl and isoaspartyl residues. This modification can change the biological activity of proteins or peptides and trigger an auto-immune response. The α-lactalbumins of members of the Camelidae family are the only of described α-lactalbumins that carry two AsnGly sequences. In the present study, high-resolution mass spectrometry, which enables accurate mass measurement has shown that Asn16 and Asn45 underwent a nonenzymatic deamidation, the sequence Asn45–Gly46 being deamidated spontaneously at near-neutral and basic pH and Asn16–Gly17 rather at basic pH. The 16–17 sequence was probably stabilized at near-neutral pH by hydrogen bonds according to the molecular modelisation performed with the camel protein.