Glycine is the simplest (and the only achiral) proteinogenic amino acid, with a hydrogen atom as its side chain. It has a role as a nutraceutical, a hepatoprotective agent, an EC 2.1.2.1 (glycine hydroxymethyltransferase) inhibitor, a NMDA receptor agonist, a micronutrient, a fundamental metabolite and a neurotransmitter. It is an alpha-amino acid, a serine family amino acid and a proteinogenic amino acid. It is a conjugate base of a glycinium. It is a conjugate acid of a glycinate. It is a tautomer of a glycine zwitterion.