Use of high-performance anion exchange chromatography with pulsed amperometric detection for O-glycan determination in yeast.

O-glycosylation is a post-translational protein modification that occurs in all eukaryotes. Yeasts have received increasing attention as a host for therapeutic protein production because of their ability to secrete high levels of recombinant protein. Because yeasts such as Pichia pastoris have been shown to O-glycosylate some proteins with varying effects on protein function, it is important to elucidate the nature of this modification. Methods that characterize O-glycosylation on a qualitative and quantitative basis are thus important when considering yeast as a host for therapeutic protein production. This protocol describes the release of O-glycans from a protein sample by -elimination under alkaline conditions using sodium borohydride and sodium hydroxide. The released O-linked oligosaccharides are subsequently processed and then separated by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). An estimation of O-glycan molar occupancy and average O-mannose chain length is ultimately derived. This protocol requires approximately 3 d for completion. This method provides an assessment of O-glycosylation and allows one to correlate the effect of O-glycosylation on protein properties.