Title : The role of N-linked glycosylation in the protection of human and bovine
lactoferrin against tryptic proteolysis
Abstract :
- Lactoferrin ( LF ) is an iron-binding glycoprotein of the innate host defence system
- To elucidate the role of N-linked glycosylation in protection of LF against proteolysis, we compared the tryptic susceptibility of human LF ( hLF ) variants from human milk, expressed in human 293(S) cells or in the milk of transgenic mice and cows
- The analysis revealed that recombinant hLF ( rhLF ) with mutations Ile130--> Thr and Gly404--> Cys was about twofold more susceptible than glycosylated and unglycosylated variants with the naturally occurring Ile130 and Gly404
- Hence, N-linked glycosylation is not involved in protection of hLF against tryptic proteolysis
- Apparently, the previously reported protection by N-linked glycosylation of hLF [van Berkel, P.H.C., Geerts, M.E.J., van Veen, H.A., Kooiman, P.M., Pieper, F., de Boer, H.A. & Nuijens, J.H. (1995) Biochem
- J. 312, 107-114] is restricted to rhLF containing the Thr130 and Cys404
- Comparison of the tryptic proteolysis of hLF and bovine LF ( bLF ) revealed that hLF is about 100-fold more resistant than bLF
- Glycosylation variants A and B of bLF differed by about 10-fold in susceptibility to trypsin
- This difference is due to glycosylation at Asn281 in bLF-A
- Hence, glycosylation at Asn281 protects bLF against cleavage by trypsin at Lys282