Odorant receptor for acetic and propionic acid. Functions as part of an olfactory receptor complex including the ionotropic receptor coreceptor Ir8a. Expressed in acetic-acid-sensing neurons in the antennal coeloconic 2 (ac2) and antennal coeloconic 3 (ac3) sensilla class of sensory hairs (at protein level). Severely reduced response to acetic and propionic acid. Belongs to the glutamate-gated ion channel (TC 1.A.10.1) family.