Purification and identification of α 2–3 linked sialoglycoprotein and α 2–6 linked sialoglycoprotein in edible bird’s nest

Abstract

The distribution of α 2–3 and α 2–6 linked sialoglycoproteins in edible bird’s nest (EBN) was analyzed by Maackia amurensis agglutinin (MAA) and Sambucus nigra agglutinin (SNA) lectin blotting. Q Sepharose Fast Flow, Superdex 75 and Sephadex G-25 columns were combined to enrich sialoglycoproteins from EBN extraction. For purification and identification of α 2–3 linked sialoglycoprotein and α 2–6 linked sialoglycoprotein, MAA-Sepharose-4B, SNA-Sepharose-4B lectin affinity chromatography and matrix-assisted laser desorption–ionization time-of-flight/time-of-flight (MALDI-TOF/TOF) tandem mass spectrometry (MS) were employed successively. The contents of protein, carbohydrate and sialic acid of EBN extraction were 65.43, 20.97 and 10.47 %, respectively; EBN extraction contained high-abundance glycoproteins with the molecular weights of 128 kDa (19.1 %), 106 kDa (18.5 %) and 43 kDa (29.4 %); the 43 kDa glycoproteins contained terminal α 2–3 and α 2–6 sialic acid linkage were successively enriched by three chromatography columns; α 2–3 linked sialoglycoprotein and α 2–6 linked sialoglycoprotein were further purified by affinity chromatography eluted with 0.3 and 0.5 M lactose, respectively. In addition, MALDI-TOF/TOF MS analysis showed that α 2–3 linked sialoglycoprotein was an acidic mammalian chitinase-like protein, and α 2–6 linked sialoglycoprotein was an acidic mammalian chitinase. This method is proved to be a simple and effective approach to purify sialoglycoproteins from high-abundance glycoproteins in EBN.