Toxoplasma gondii: Purification and Characterization of an Immunogenic Metallopeptidase

Berthonneau, J., Rodier, M. H., El Moudni, B., and Jacquemin, J. L. 2000. Toxoplasma gondii: Purification and characterization of an immunogenic metallopeptidase. Experimental Parasitology95, 158–162. A Toxoplasma gondii aminopeptidase specific for the fluorogenic substrate L -arginine 7-amino-4-methylcoumarin was identified in cell-free extract. This enzyme was purified by high-performance liquid chromatography using first size exclusion, then anion exchange, followed by a second size exclusion. The purified enzyme exhibited a pl of 4.7 by chromatofocusing and had an apparent molecular weight of 110 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. The purification factor was 80.9 and the yield was 14%. The optimal activity was at pH 7.4 and was strongly inhibited by EDTA and o-phenanthroline. Antibodies against this T. gondii metallopeptidase were detected by immunoprecipitation and immunoblotting in human sera obtained from patients undergoing toxoplasmosis.