One of the nonessential amino acids , closely related to glutamine .
The two constitute a substantial fraction of the amino acids in many protein s (1020% in many cases and up to 45% in some plant proteins). An important metabolic intermediate as well as a neurotransmitter molecule in the central nervous system, glutamic acid finds uses in medicine and biochemical research. Its sodium salt is the food flavour enhancer monosodium glutamate (MSG).