Probable inactive serine protease which plays a role in ookinete traversal of the mosquito host midgut epithelium. Predominantly, localizes in the anterior part of the ookinete (PubMed:29873127). May localize to the secretory compartments (PubMed:29873127). Expressed in ookinetes (at protein level). Ookinetes fail to traverse the midgut epithelium resulting in a reduced number of oocysts in the gut epithelium of the mosquito host A.stephensi (PubMed:29873127). Gametogenesis and ookinete development are normal (PubMed:29873127). Growth rate and development of blood stage parasites are normal (PubMed:29873127). Belongs to the peptidase S8 family. In contrast to other members of the peptidase S8 family, contains Gly and Glu residues at the position of the canonical catalytic Asp and His, respectively, suggesting that the protein lacks protease activity.