Glutamic acid and glutamate are the chemical names for two very similar substances. You consume glutamate when you take in protein -- glutamate is a constituent of protein -- or when you eat food that contains monosodium glutamate. Because of the similarities between the chemicals, scientists often call glutamate "glutamic acid."
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Glutamic acid is the formal name for one of the 20 amino acids, which are the building blocks of proteins. Each amino acid has a central carbon atom, to which four different groups are bonded. These groups include a hydrogen atom, a group called an amine, a group called a carboxylate and a variable side chain. The composition of the side chain determines the identity of the amino acid. In the case of glutamic acid, the side chain has the formula CH2CH2COOH.
The suffix "ate" in chemistry generally indicates an acid that has lost a hydrogen atom. When glutamic acid, which is acidic, loses a hydrogen from its side chain, it becomes glutamate, with a side chain composed of CH2CH2COO. In the human body, glutamic acid almost always exists as glutamate, because conditions in the body favor the loss of the hydrogen atom from glutamic acid, explain Drs. Reginald Garrett and Charles Grisham in their book "Biochemistry."
Little difference exists between the behavior of glutamic acid and the behavior of glutamate. In fact, the chemicals are so similar in behavior and function that it's quite common for chemists to refer to glutamate in the body as "glutamic acid" even if the acid has lost a hydrogen. With regard to function in the body, think of glutamate and glutamic acid as completely equivalent or interconvertible.
Uses of Glutamate
Your body uses glutamic acid or glutamate for a variety of purposes. You can burn the compound for cellular energy, as you can burn any of the amino acids for cellular energy, explain Drs. Mary Campbell and Shawn Farrell in their book "Biochemistry." You can also use glutamate to help in the disposal of nitrogen, a metabolic waste product of protein metabolism. Finally, glutamate is an important neurotransmitter, or chemical signaling molecule.
Glutamate also finds application in the food industry, one of the few cases in which the distinction between glutamic acid and glutamate is quite important. Glutamate can form a type of chemical bond to a particle of sodium, while glutamic acid can't. As such, it's possible to make the compound MSG, but there's no way to combine sodium with glutamic acid. In the food industry, MSG is a flavoring agent common in Chinese food.