Enzymic removal of two oligosaccharide chains from ricin B-chain

Peptide:N-glycosidase F removed both the asparagine-linked oligosaccharide chains of ricin B-chain in the absence of lactose. In the presence of lactose, which binds specifically to the B-chain, only one oligosaccharide chain was removed. Lactose also protected Ricinus communis agglutinin B-chain against the removal of one of the two susceptible oligosaccharides present in each B-chain subunit.