The protein encoded by this gene is member of the GAP1 family of GTPase-activating proteins. These proteins stimulate;the GTPase activity of normal RAS p21 but not its oncogenic counterpart. Acting as a suppressor of RAS function, the;protein enhances the weak intrinsic GTPase activity of RAS proteins resulting in the inactive GDP-bound form of RAS,;thereby allowing control of cellular proliferation and differentiation. This particular family member contains domains;which are characteristic of the GAP1 subfamily of RasGAP proteins but, in contrast to the other GAP1 family members,;this protein is strongly and selectively expressed in endocrine tissues. Alternatively spliced transcript variants;that encode different isoforms have been described.