Detection of a glycosylated form of hen egg white lysozyme

By assaying lysozyme activity after denaturing polyacrylamide gel electrophoresis of commercial hen egg white lysozyme preparations, minor lysozymal activity was detected as an 18-kDa protein. After electrophoretic purification for microsequencing, the N-terminus sequence of the 18-kDa lysozyme was found to be identical with mature 14.4-kDa hen egg white lysozyme. The 18-KDa hen egg white lysozyme was judged to be glycosylated based on 3.6-kDa decrease in molecular mass after N-glycosidase F treatment, binding to concanavalin A-Sepharose, and staining with periodate-Schiff's reagent. The minor form corresponded to about 0.3% of lysozyme molecules.