N-Acetyl Glucosamine (N-A-G) is a precursor to hyaluronic acid, which is part of the synovial fluid in joints. N-A-G combines with mucin secreted from goblet cells to support the glycocalyx, a protective layer of glycoproteins and polysaccharides that lines the digestive tract. N-A-G is an aminosaccharide, synthesized from glucose and the amino acid L-glutamine, that has been stabilized by complexing it to an acetyl group.