11. What is the A1 antigen?
From Quiz Red Cell Antigens
Answer:
N-acetyl-D-galactosamine
D-galactose is the B antigen. Both A1 and B are part of the ABO blood group system, the most important in transfusion medicine.
Acetylcholinesterase, an enzyme primarily known to degrade acetylcholine, exists as a dimer on the red cell surface and forms what is known as the Cartwright antigen. The Cartwright blood system has two antithetical antigens, Yt(a) and Yt(b), formed by an amino acid substitution at position 353 of histidine (Yt(a)) and asparagine (Yt(b)). The enzyme is active on the red cell membrane, however its function in this setting is unknown.
As a trivia note, a form of acetylcholinesterase is found in the Pacific Torpedo ray, Torpedo californica.
Glycophorin A is one half of the MNSs (more strictly, the MNS) blood group system, the M and N antigens. Glycophorin B forms the S and s antigens. The M and N antigens are a result of two amino acid substitutions. The M antigen has a serine and glycine and positions 1 and 5, respectively, while the N antigen has leucine and glutamic acid.