Purification and characterisation of a serine-type protease from Eimeria tenella oocysts

Homogenates of sporulated oocysts of E. tenella have detectable proteolytic activity which is completely inhibited by phenylmethylsulfonyl fluoride and L-trans-epoxysuccinyl-leucyl-amido-(4-guanidino)-butane, indicating the presence of both serine and cysteine-type proteases in sporulated oocysts. A serine-type protease has been purified from the homogenate using immobilised-bacitracin affinity chromatography. The monomeric enzyme had an apparent M(r) of 20,000 and a pI of 8.6. The maximum proteolytic activity with azocasein and gelatin was observed at pH 8.0. Antibodies raised in rabbits and chickens against purified protease recognised this protein on blots of sporozoite homogenates.