Blastocystis is the most common eukaryotic parasite of the human gastrointestinal tract. Its pathogenicity remains a matter of debate, however, many recent studies suggest that this organism is a pathogen. Some authors reported that cysteine protease plays important role in the pathogenicity of Blastocystis spp. The study investigated the protease activity of Blastocystis isolates obtained from stool samples of symptomatic and asymptomatic individuals using gelatin SDS-PAGE and azocasein assay. The present study was carried out on 62 subjects positive for Blastocystis whetherpresentingwith gastrointestinal symptoms or not. The symptomatic group (cases, GI) included 42 cases while the asymptomatic (control, GII) group included 20 subjects.
               Using gelatin SDS-PAGE analysis, the protease profiles of Blastocystis isolates showed 14 protease bands of both high and low molecular weights with significant differences between symptomatic and asymptomatic groups at 35, 60 and 140 kDa MW bands. Statistical analysis of the protease profile of Blastocystis isolates showed a significant difference (P value < 0.05) between the two groups. Using Azocasein assay, Blastocystis isolatesfrom symptomatic cases show quantitatively higher protease activity than asymptomatic cases but without significant difference between both groups.