Purification and Partial Biochemical Characterization of Glycoproteins in a Champenois Chardonnay Wine

Abstract

Seven proteins have been isolated from a champenois Chardonnay still wine by concanavalin A affinity chromatography. The proteins of 24/25, 30 and 60/64 kDa are then purified by preparative isoelectric focusing (pH gradient 2.5−5) and by preparative SDS−PAGE. The 30 kDa protein presents a low hydrophobicity (780 cal/amino acid residue), a homogeneous molecular weight, and an isoelectric point close to 2.5. It also has the characteristic of being retained by Lens culinaris agglutinin (LCA). Proteins of 24/25 and 60/64 kDa present heterogeneous MW, a p I close to 3.9, and a hydrophobicity 30% superior to that of the 30 kDa molecule. Moreover, these two proteins are not retained by LCA. The three analyzed proteins are not susceptible to O -glycosidase activities. In return, the 24/25 kDa protein undergoes a 3100 Da variation after treatment with the peptide- N -glycanase F: it is a true N -glycosyl protein. The comparison of the must and the corresponding wine proteic fractions isolated by concanavalin A shows that the two heterogeneous MW molecules (24/25 and 60/64 kDa) originate from the grape berry. In addition, they suffer no modification during the alcoholic fermentation. Keywords: Wine; glycoproteins; affinity chromatography; foam stabilizer; must; hydrophobicity