Plasmodium falciparum: isolation and characterization of a 55-kDa protease with a cathepsin D-like activity from P. falciparum.

Native electrophoresis followed by imprint digest method using hemoglobin as substrate allowed the detection of parasite hemoglobinase activity at acidic pH (3.9 to 5). This protease was inhibited specifically by pepstatin A and insensitive to other protease inhibitors. The molecular weight determination using modified SDS-PAGE followed by imprint digest method, demonstrated a single area of activity at 55-58 kDa, similar to cathepsin D characterized in eucaryotic cells. The parasitic origin has been shown by radiolabeling experiments with [35S]-methionine. The 55-kDa protein was immunoprecipitated by a rabbit anti-cathepsin D serum.