The ionic form of the most abundant amino acid in the human body (glutamic acid). Glutamate plays roles in many aspects of physiology and is best known for its role as a neurotransmitter in the brain and peripheral nervous system. Abnormal levels of glutamate have been linked to depression and schizophrenia. The amino acid is a component of the antioxidant glutathione, and (little known fact) its anion is what gives MSG (monosodium glutamate) and various foods their “umami” flavor.