GTPase-activating protein. Directly and specifically regulates the adapter protein 3 (AP-3)-dependent trafficking of proteins in the endosomal-lysosomal system (By similarity). Homodimer. Interacts with several subunits of the AP-3 protein complex (By similarity). Associates with the endocytic compartment. The PH domain mediates AP-3 binding. Belongs to the centaurin gamma-like family.