Mutation at codon 322 in the human acetylcholinesterase (ACHE) gene accounts for YT blood group polymorphism.

Acetylcholinesterase is present in innervated tissues, where its function is to terminate nerve impulse transmission. It is also found in the red blood cell membrane, where its function is unknown. We report the first genetic variant of human acetylcholinesterase and support the identity of acetylcholinesterase as the YT blood group antigen. DNA sequencing shows that the wild-type sequence of acetylcholinesterase with His322 (CAC) is the YT1 blood group antigen and that the rare variant of acetylcholinesterase with Asn322 (AAC) is the YT2 blood group antigen. Two additional point mutations in the acetylcholinesterase gene do not affect the amino acid sequence of the mature enzyme.