Catalyzes the reversible synthesis of acetylcholine (ACh) from acetyl CoA and choline at cholinergic synapses.

(UniProt, P07668)

Probable structural gene for choline acetyl transferase [ChAT, acetyl CoA-choline-O-acetyltransferase (EC 2.3.1.6)], which has been purified and whose molecular weight approximates 67 kilodaltons (Slemmon, Salvaterra, Crawford and Roberts, 1982, J. Biol. Chem. 257: 3847-52); monoclonal antibodies prepared and inhibit enzyme (Crawford, Slemmon, and Salvaterra, 1982, J. Biol. Chem. 257: 3853-56); homozygotes and hemizygotes for either of the original two non-conditionally mutant alleles, Chal1 or Chal2, show no detectable enzymatic activity as late embryos, which is when the mutants die; other non-conditional lethals at the locus not tested for lethal stage or ChAT activity; either of two temperature sensitive alleles, Chats1 or Chats2, causes a variety of phenotypic defects when hemizygous or homozygous: reduced viability at 25 and death at 29 (Chats1), reduced viability at 18 and death at 22 or above (Chats2) plus gradual but reversible decline of enzymatic activity and of acetylcholine levels following transfer of low-temperature reared Chats adults to 29-30 or above (Greenspan, 1980; Salvaterra and McCaman, 1985, J. Neurosci. 5: 903-10); correlated with decrements in these biochemical parameters (reversible on lowering temperature), are heat-induced abnormalities of general mobility, male courtship ability, plus electroretinogram (Greenspan, 1980), landing response (Gorczyca and Hall, 1985, Neurosci. Abstr. 11: 512), and of several elements of physiological responses made by thoracic indirect flight muscles following stimulation of giant fiber pathway, implying that certain interneuronal synapses in this pathway are cholinergic (Gorczyca and Hall, 1984, J. Neurogenet. 1: 289-313); whereas wild type exhibits two molecular forms of ChAT activity after isoelectric focusing, homogenates of Chats1 lead to a single form, and of Chats2 to two forms shifted to higher-than-normal pI (Salvaterra and McCaman, 1985); these two conditional Cha mutations also cause ChAT activity to have accentuated thermolability in vitro (Greenspan, 1980; Salvaterra and McCaman, 1985). Immunohistochemical staining of ChAT reveals wide distribution in CNS; this staining is strong in Chats1 at permissive temperature but diminishes after in-vivo heat treatment (Gorczyca and Hall, 1987, J. Neurosci. 7: 1361-69); Chats2 staining is poor even at permissive temperature and diminishes after heating the flies (Gorczyca and Hall, 1987). In situ hybridization to tissue sections detected transcriptional activity in most neuronal elements of the cell-rich areas of the cortical regions of the cerebrum and optic lobes; however, some cells in the lamina including the amacrine neurons showed no label. Highest expression is seen in laminar monopolar-cell region, and the cerebral cortical rind, and to a lesser degree, over cortical cells of medulla-lobula, the antennal sensory neurons, and the retinular-cell layer of the compound eye (Barber, Sugihara, Lee, Vaughn, and Salvaterra, 1989, J. Comp. Neurol. 280: 533-43). Immunolocalization of ChAT in the adult cephalic ganglion reveals weak staining in the lamina corresponding to the synaptic layer of photoreceptor cells 1-6 of the ommatidia, three layers of strong reaction corresponding to the synaptic layers in the medulla, and labeling of four layers in the lobula (Ikeda and Salvaterra, 1989, J. Comp. Neurol. 280: 283-90). In Chats1 staining seen at 19 but disappears by 120 hours after shift to 30; Chats2 shows reduced staining at 19 and none after 80 hours at 30.