Differential sensitivity of d-galactose-binding lectins from fruits of dwarf elder (Sambucus ebulus L.) to a simulated gastric fluid

Some lectins from Sambucus spp. share amino acid sequences with the pollen Sam n1 allergen. The lectins ebulin f and SELfd from the early stages of growth were isolated and subjected to analysis by MALDI-TOF mass spectrometry, tryptic peptide fingerprinting, molecular characterization and pepsin digestibility. The molecular mass (33.214) and other structural features of the Sam n1 allergen fit best with a monomeric lectin like SELlm (Mr 34.2 kDa) found in shoots of dwarf elder. Ebulin f toxicity to mice was higher intraperitoneally than orally at the same dose (5 mg/kg body weight). In contrast SELfd at the same dose lacks of apparent toxicity. Ebulin f, but not SELfd, undergoes extensive pepsin proteolysis, which could explain the differences in toxicity. The present study supports our hypothesis that the Sam n1 allergen could be a sequence-related monomeric lectin like SELlm present in shoots of Sambucus ebulus rather than ebulin.