Serine proteases are important virulence factors for many pathogens. Recently， we discovered a group of trypsin-like serine proteases with domain organization unique to flatworm parasites and containing a thrombospondin type 1 repeat (TSR-1). These proteases are recognized as antigens during host infection and may prove useful as anthelminthic vaccines， however their molecular characteristics are under-studied. Here， we characterize the structural and proteolytic attributes of serine protease 2 (SmSP2) from Schistosoma mansoni， one of the major species responsible for the tropical infectious disease， schistosomiasis.