Title : N-glycosylation microheterogeneity and
site occupancy of an Asn-X-Cys
sequon in plasma-derived and recombinant
protein C . Human
protein C (hPC) is glycosylated at three
Asn-X-Ser/Thr and one atypical
Asn-X-Cys sequons
Abstract :
- We have characterized the micro- and macro-heterogeneity of plasma-derived hPC and compared the glycosylation features with recombinant protein C ( tg-PC ) produced in a transgenic pig bioreactor from two animals having approximately tenfold different expression levels
- The N-glycans of hPC are complex di- and tri-sialylated structures , and we measured 78% site occupancy at Asn-329 (the Asn-X-Cys sequon )
- The N-glycans of tg-PC are complex sialylated structures , but less branched and partially sialylated
- The porcine mammary epithelial cells glycosylate the Asn-X-Cys sequon with a similar efficiency as human hepatocytes even at these high expression levels, and site occupancy at this sequon was not affected by expression level
- A distinct bias for particular structures was present at each of the four glycosylation sites for both hPC and tg-PC
- Interestingly, glycans with GalNAc in the antennae were predominant at the Asn-329 site
- The N-glycan structures found for tg-PC are very similar to those reported for a recombinant Factor IX produced in transgenic pig milk, and similar to the endogenous milk protein lactoferrin , which may indicate that N-glycan processing in the porcine mammary epithelial cells is more uniform than in other tissues