Analysis of Minor Acidic N-Glycans in Human Serum

Prior investigations by our research group focused on the method development for the simultaneous analysis of sulfated and phosphorylated glycans. Herein, the developed method was applied to analyze minor acidic N-glycans including sulfated and phosphorylated N-glycans in human serum. First, 2-aminobenzoic acid-labeled minor acidic N-glycans were enriched from the serum using a serotonin-immobilized column and were then separated into groups using hydrophilic interaction liquid chromatography, and analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Phosphorylated hybrid-type and sulfated bi-antennary N-glycans were detected in the serum. In addition, we observed that multiple types of glucuronidated N-glycans were present. These results indicate that the developed method is applicable to the analysis of glucuronidated as well as sulfated and phosphorylated N-glycans. It was also applied to the sera obtained from 17 healthy subjects and 15 pancreatic cancer patients, and the profiles of sulfated, phosphorylated, and glucuronidated N-glycans were compared. The expressed amount of glucuronidated N-glycans was significantly decreased in some pancreatic cancer patients. Numerous examples of the N-glycan analysis in human serum were reported, but phosphorylated and glucuronidated glycans were not investigated. The methods described herein allow the analysis of minor acidic glycans that are typically difficult to detect.