Removal of the N-glycan from the concanavalin A (Con A) glycoprotein precursor is a key step in its conversion into an active lectin. N-Glycanase (EC 3.5.1.52), the enzyme from jackbean catalysing this process, has been purified to homogeneity as judged by native PAGE. One of the purification steps is binding of the enzymic activity to Con A-Sepharose and its elution by methyl α-mannoside. On SDS/PAGE the principal components were found to be 78 kDa, 74 kDa, 54 kDa, 32 kDa and 30 kDa polypeptides. These did not react with Con A on an affinity blot. Cleveland mapping indicated that some of these polypeptides had related primary structures. The enzyme has a broad pH optimum in the region of 5.0.