Catalytic subunit of the heterodimeric RalGAP2 complex which acts as a GTPase activator for the Ras-like small GTPases RALA and RALB. Component of the heterodimeric RalGAP2 complex with RALGAPB. Heterodimerization is required for activity (By similarity). Abundantly expressed in testis, pancreas, lung, thymus, brown fat, and white fat. Extended N-terminus. Probable cloning artifact leading to erroneous C-terminus.