The cysteine proteinases have a potential role in host-parasite interaction and virulence. Predominantly expressed by stumpy forms, which are preadapted for differentiation into procyclic trypanosomes in the tse-tse midgut. The 108-residue extension appears likely to be processed in part to produce the mature enzyme, and may be involved in targeting the protein within the cell. Belongs to the peptidase C1 family.