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