CHAT (Choline Acetyltransferase): CHAT is the enzyme responsible for producing acetylcholine, a key neurotransmitter in both the peripheral and central nervous systems. Acetylcholine plays a crucial role in muscle contraction, heart rate regulation, memory, and learning. Changes in CHAT activity that disrupt acetylcholine synthesis are associated with neurological disorders such as Alzheimer’s disease and myasthenia gravis.