positively regulates GTPase activity GTPase activator activity Sar GTPase activator activity Rac GTPase activator activity Ral GTPase activator activity Ras GTPase activator activity RanGAP GAP activity Rho GTPase activator activity Rab GTPase activator activity Ran GTPase activator activity Rap GTPase activator activity ARF GTPase activator activity enzyme activator activity GTPase regulator activity