GTPase-activating protein (GAP) for ADP ribosylation factor 1 (ARF1). Hydrolysis of ARF1-bound GTP may lead to dissociation of coatomer from Golgi-derived membranes to allow fusion with target membranes. GAP activity stimulated by phosphatidylinositol 4,5-bisphosphate (PIP2). Also found on peripheral punctate structures likely to be endoplasmic reticulum-Golgi intermediate compartment. Widely expressed. Highest expression in endocrine glands (pancreas, pituitary gland, salivary gland, and prostate) and testis with a much higher expression in the testis than in the ovary. Expressed at higher level in adult thymus, brain and lung, than in corresponding fetal tissues. Expressed at lower level in spleen, heart, kidney and liver during development. Was originally termed ARFGAP1. Truncated N-terminus. Truncated N-terminus.