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 (By similarity). Interacts with the AP-1 complex (By similarity). Co-localizes with AP-1 in the trans-Golgi network (By similarity). Co-localizes with MAP2 and ACTB on the cytoskeleton (By similarity). Co-localizes with STX6 and GOSR2 at the Golgi apparatus (By similarity). Belongs to the peptidase S9A family.