title: Sm22.6 antigen is an inhibitor to human thrombin.
abstract: The physiological role of Schistosomiasis mansoni 22.6 antigen (sm22.6 Ag) and its pathogenic effect on the human host has never been reported. Recombinant sm22.6 Ag is a homogenous polymer under non-denaturing/non-reducing conditions, and an inhibitor to human thrombin. Kinetic and Western blot assays show that the recombinant protein interacts with human thrombin and inhibits proteolytic activity of the protease. Tests of whole blood revealed that coagulation time was significantly delayed (3-5 times longer) in the presence of the recombinant protein at a concentration similar to thrombin in normal blood samples. Kinetic studies revealed that the delayed coagulation time was due to the inhibition of alpha-thrombin proteolytic activity by the parasite protein in an irreversible pattern, and a reversible inhibition to gamma-thrombin. Also, Western blot analysis under non-denaturing/non-reducing conditions showed that sm22.6 Ag binds to both alpha- and gamma-thrombin. Our results strongly suggest that sm22.6 antigen plays a role in down-regulation of coagulation in humans.
authors.affiliation: Department of Parasitology, China Medical University School of Medicine, Taichung, 92 Hseu-shi road, Taichung, Taiwan, ROC.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Lin
authors.forename: Shiping
authors.initials: S
authors.lastname: He
mesh_terms: D000818:Animals; D000925:Anticoagulants / Q000378:metabolism / Q000494:pharmacology*; D000947:Antigens, Helminth / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D011817:Rabbits; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012550:Schistosoma mansoni / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity*; D013917:Thrombin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D000947:Antigens, Helminth; D011994:Recombinant Proteins; D013917:Thrombin