Indeed, it has been shown that legumain can degrade fibronectin, an extracellular matrix glycoprotein. Genes coding for protease inhibitors Paclitaxel human endothelial cells are also present in the Blastocystis sp. Inhibitors,Modulators,Libraries genome, and some are predicted to be secreted. Release of protease inhibitors may weaken the host response as described in nematodes. Blastocystis sp. encodes three protease inhibitors cystatin, type1 proteinase inhibitor and endopeptidase inhibitor like protein. Type1 proteinase inhibitor is similar to chymotrypsin inhibitor, which is known to inactivate intestinal digestive enzymes as in Ascaris suum, thus protecting the parasite against non specific digestive defenses. Cysta tin, also called stefin, was described in Fasciola gigantica and shown to inhibit mammalian cathepsin Inhibitors,Modulators,Libraries B, cathe psin L and other cysteine proteases, including parasite ones.

In Blastocystis sp. secreted cystatin could participate in the regulation of parasitic cysteine protease activities. Cystatin can also potentially inhibit host proteases involved in MHC II antigen processing and presentation, including the key enzyme asparaginyl endopeptidase and Inhibitors,Modulators,Libraries cathe psin S, the mammalian legumain. Interestingly, Inhibitors,Modulators,Libraries a putative type I polyketide synthase gene was also found in the Blastocystis sp. genome, potentially originating from HGT. PKS and non ribosomal peptide synthetase synthesize metabolites like simple fatty acids, but also a myriad of chemical structures that possess important pharmacolo gical activities and environmental impact, such as toxins, antibiotics or antimicrobials.

Inhibitors,Modulators,Libraries Type I PKS was formerly known only from bacteria and fungi, but recently homo logous genes were also discovered in some protists. According to the Database for NRPS and PKS, the Blastocystis sp. PKS gene possesses the three essential domains, and three other domains dehydratase, ketoacyl reductase, and enoyl reductase domains. The presence of these additional domains would permit this organism to synthesize both reduced polyketides and fatty acids. Domain comparison with other type I PKSs suggests that Blastocystis sp. PKS is similar to type I PKS from the ascomycete Cochliobolus heterostrophus, a maize pathogen that produces T toxin, a polyketide mole cule that disturbs mitochondria by binding a protein of the inner mitochondrial membrane. Searching polyke tide related metabolites in the secretome of Blastocystis sp.

would be of interest in order to identify molecules that could have effects on the host. Antioxidant system and multi drug resistance Like other anaerobic organisms, Blastocystis sp. has to eliminate toward reactive oxygen species such as superoxide anions, hydrogen peroxide and hydroxyl radicals resulting from metabolism. In addition, this microorganism has to cope with the oxidative burst imposed by host immune cell effectors.