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Choline acetyltransferase
Choline acetyltransferase (commonly abbreviated as ChAT, but sometimes CAT) is a transferase enzyme responsible for the synthesis of the neurotransmitter acetylcholine. ChAT catalyzes the transfer of an acetyl group from the coenzyme, acetyl-CoA, to choline yielding acetylcholine (ACh). ChAT is found in high concentration in cholinergic neurons, both in the central nervous system (CNS) and peripheral nervous system (PNS). As with most of nerve terminal proteins, ChAT is produced in the body of the neuron and is transported to the nerve terminal, where its concentration is highest. Presence of ChAT in a nerve cell classifies this cell as a "cholinergic" neuron. In humans, the choline acetyltransferase enzyme is encoded by the ''CHAT'' gene.
== History ==
Choline acetyltransferase was first described by David Nachmansohn and A. L. Machado in 1943. A German biochemist, Nachmansohn had been studying the process of nerve impulse conduction and utilization of energy-yielding chemical reactions in cells, expanding upon the works of Nobel laureates Otto Warburg and Otto Meyerhof on fermentation, glycolysis, and muscle contraction. Based on prior research showing that "acetylcholine’s actions on structural proteins" were responsible for nerve impulses, Nachmansohn and Machado investigated the origin of acetylcholine.
::''“An enzyme has been extracted from brain and nervous tissue which forms acetylcholine. The formation occurs only in presence of adenosinetriphosphate (ATP). The enzyme is called choline acetylase.” -Nachmanson & Machado, 1943''〔
The acetyl transferase mode of action was unknown at the time of this discovery, however Nachmansohn hypothesized the possibility of acetylphosphate or phosphorylcholine exchanging the phosphate (from ATP) for choline or acetate ion.〔 It was not until 1945 that Coenzyme A (CoA) was discovered simultaneously and independently by three laboratories, Nachmansohn's being one of these. Subsequently acetyl-CoA, at the time called “active acetate,” was discovered in 1951. The 3D structure of rat-derived ChAT was not solved until nearly 60 years later, in 2004.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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