Probable serine protease, which plays a crucial role in the fertility of male mice including sperm migration and sperm-egg interaction (PubMed:30032357). Mainly observed in the luminal side of seminiferous tubules and sperm acrosome. Expressed in adult mouse testis. Deficient male display infertility with impaired sperm migration from uterus into oviduct and defective sperm-zona and sperm-egg recognition/binding. However, the mating activity, sperm production, sperm morphology, sperm motility, inducibility of AR, activity of acrosomal enzymes and in vitro sperm fertility are almost normal. Male show an absence of mature ADAM3 in sperm. Belongs to the peptidase S1 family. Controversial data exist concerning the topology of PRS55. One study in mouse shows that PRSS55 is a GPI-anchored protein (PubMed:30032357). An other study does not confirm the GPI-anchor status of PRSS55 (By similarity). However, as a GPI-anchor motif is detected, the possibility of a GPI-anchor instead of a single-pass type I membrane protein is probable.