Secreted acid phosphatase of Leishmania mexicana: a filamentous phosphoglycoprotein polymer.

In the promastigote, or insect stage, most species of the parasitic protozoan Leishmania secrete an acid phosphatase. The enzyme purified from the culture medium of Leishmania mexicana is shown to be a complex [13.3% (wt/wt) protein, 74.4% (wt/wt) carbohydrate, and 12.3% (wt/wt) phosphate] composed of a predominant phosphorylated glycoprotein with a relative molecular mass of 100 kDa and noncovalently associated high molecular mass (proteo)phosphoglycans. Electron microscopy discloses long filaments composed of a central chain of protein subunits surrounded by a diffuse glycocalix that can be decorated by monoclonal antibodies or concanavalin A. In contrast to the polymeric structure of the L. mexicana enzyme, the acid phosphatase secreted by Leishmania donovani is mono- or oligomeric but not filamentous.