Serine peptidase whose precise substrate specificity remains unclear (By similarity). Does not cleave peptides after a arginine or lysine residue (By similarity). Regulates trans-Golgi network morphology and sorting by regulating the membrane binding of the AP-1 complex (By similarity). May play a role in the regulation of synaptic vesicle exocytosis (By similarity). Homodimer. Belongs to the peptidase S9A family.