Purification and characterisation of a secreted aminopeptidase from adult Ascaris suum

A metalloaminopeptidase was identified in culture fluids collected during in vitro cultivation of adult Ascaris suum. The enzyme was purified by anion-exchange and size-exclusion HPLC. The M(r) of the enzyme was estimated at 293 kDa and consisted of subunits with M(r)s of 153 and 142kDa. The isoelectric point of the aminopeptidase was 4.7. The aminopeptidase displayed a substrate preference for terminal arginyl residues. Aminopeptidase activity was also present in muscle, female reproductive tissue, pharynx, pseudocoelomic fluid and intestine. Among the various tissues, aminopeptidase activity was highest in the intestines; the highest activity was found in culture fluids (three-fold higher than intestinal tissue). The aminopeptidase released by adult A. suum was enzymatically and biochemically identical to an aminopeptidase released during in vitro development of A. suum third- to fourth-stage larvae.