Structural characterization of N-glycans of cauxin by MALDI-TOF mass spectrometry and nano LC-ESI-mass spectrometry

Cauxin is a carboxylesterase-like glycoprotein excreted as a major component of cat urine. Cauxin contains four putative N-glycosylation sites. We characterized the structure of an N-linked oligosaccharide of cauxin using nano liquid chromatography (LC)-electrospray ionization (ESI) and matrix-assisted laser desorption/ ionization quadrupole ion trap time-of-flight mass spectrometry (MALDI-QIT-TOF MS) and MS/MS, and high-performance liquid chromatography (HPLC) with an octadecylsilica (ODS) column. The structure of the N-linked oligosaccharide of cauxin attached to (83)Asn was a bisecting complex type, Gal beta 1-4GlcNAc beta 1-Man alpha 1-3(Gal beta 1-4GlcNAc beta 1-2Man alpha 1-6)(GlcNAc beta 1-4)- 2Man alpha 1-4GlcNAc beta 1-4(Fuc alpha 1-6)GlcNAc.