N-Acetylgalactosamine

N-Acetylgalactosamine (also called GalNAc, 2-Acetamido-2-deoxy-D-galactopyranose or N-Acetyl-D-galactosamine) is a monosaccharide derivative of galactose.

Function
In humans it is the terminal carbohydrate forming the antigen of blood group A.

It is typically the first monosaccharide that connects serine or threonine in particular forms of protein O-glycosylation.

N-Acetylgalactosamine is necessary for intercellular communication, and is concentrated in sensory nerve structures of both humans and animals.