Analysis of plant glycoproteins by matrix-assisted laser desorption ionisation mass spectrometry: Application to the N-glycosylation analysis of beanphytohemagglutinin

Matrix-assisted laser desorption ionisation-time of flight (MALDI-TOF) spec trometry is a recently developed soft ionisation mass spectrometry techniqu e which appears as a highly efficient tool for the N-glycosylation analysis of glycoproteins. The potentiality of this analytical technique is illustr ated through the analysis of the N-glycosylation of the isolectin L of bean phytohemagglutinin (PHA-L). The analysis was carried out on the native PHA -L as well as on the N-glycans released from this lectin. Furthermore, the two glycopeptides containing the potential N-glycosylation sites prepared b y proteolytic cleavage of PHA-L and purified by HPLC were analysed by MALDI -TOF This study has confirmed that PHA-L is N-glycosylated by two populatio ns of oligosaccharides, high-mannose-type N-glycans and paucimannosidic-typ e N-glycans, located on Asn-12 and Asn-60, respectively, and has pointed ou t the microheterogeneity of the glycans N-linked on both Asn residues. (C) Elsevier, Paris.