Glycine, NH2CH2COOH, is the simplest amino acid. It is colorless, crystalline, water soluble, and amphoteric because it has both the amine group (-NH2, basic) and the carboxylate group (-COOH, acidic). In acidic solutions it behaves as a base to form the +H3NCH2COOH ion; in basic solutions it acts as an acid to form the H2NCH2COO- ion. In neutral solutions, the ion +H3NCH2COO- can exist .
Glycine is a common residue in proteins, especially collagen and elastin and is not optically active. It is also a major inhibitory neurotransmitter in the spinal cord and brainstem of the vertebrate central nervous system.