Catalyzes a cyclopropane ring-opening reaction, the irreversible conversion of 1-aminocyclopropane-1-carboxylate (ACC) to ammonia and alpha-ketobutyrate. Allows growth on ACC as a nitrogen source. 1-aminocyclopropane-1-carboxylate + H2O = 2-oxobutanoate + NH4(+) Homotrimer. Introduced by genetic manipulation and expressed in improved ripening tomato by Monsanto. ACC is the immediate precursor of the phytohormone ethylene which is involved in the control of ripening. ACC deaminase reduces ethylene biosynthesis and thus extends the shelf life of fruits and vegetables. Belongs to the ACC deaminase/D-cysteine desulfhydrase family.