An enzyme producing isoprimeverose from xyloglucan fragment oligosaccharides has been purified to the electrophoretically pure state from a commercial enzyme preparation of Aspergillus oryzae (Sanzyme 1000). The purified enzyme showed approximately 1,280-fold increase of the specific activity over the original preparation. The purified enzyme was shown to be an oligomeric protein consisting of two subunits, each of which had a molecular weight of 115,000. The enzyme showed the highest activity at pH 5.0 and 60 degrees C, and was stable in the pH range from 5 to 7 and at up to 50 degrees C. The isoelectric point of this enzyme was pH 3.9. The purified enzyme was highly specific for xyloglucan fragment oligosaccharides and split off isoprimeverose units from the non-reducing end of the backbone of the substrate.