glutamic acid
Meaning of glutamic acid: A protein building block that doubles as the brain's main go signal, and as the flavor behind monosodium glutamate.
Definition of glutamic acid
Glutamic acid is one of the twenty amino acids that cells string together to build proteins. The body makes its own supply, so it does not have to come from food. In the charged form it takes inside the body, called glutamate, it is also the main excitatory messenger of the brain and a hub in the handling of nitrogen left over from protein breakdown.
What does it do in the body?
Glutamic acid is an amino acid, one of the small molecules that link end to end to form proteins. Beyond that structural job it sits at a chemical crossroads. It accepts and hands off nitrogen, which is how the body shuffles amino groups between molecules and prepares waste nitrogen for disposal in urine. Converted to a related compound, it feeds the energy cycle inside cells. In the nervous system it is the messenger that switches other nerve cells on.
How does it work in the brain?
Most signals that excite a nerve cell in the brain and spinal cord are carried by glutamate. One cell releases it, receptors on the next cell respond, and the message moves along. Supporting cells then mop it up quickly, and that clearance matters. When too much glutamate lingers, as it can after a stroke or a head injury, receiving cells are driven too hard and die. Researchers call this excitotoxicity. It is the reason several medicines aim to damp glutamate signaling rather than raise it.
Is the glutamate in food the same thing?
| Form | Where it is found | What it does there |
|---|---|---|
| Free glutamate | Aged cheese, tomatoes, mushrooms, soy sauce | Produces the savory taste called umami |
| Monosodium glutamate | Added to food as a seasoning | The sodium salt of the same molecule |
| Bound glutamate | Locked inside dietary protein | Released only during digestion |
Chemically these are the same substance. The gut burns most swallowed glutamate as fuel for its own lining, and little reaches the brain, since the blood brain barrier restricts entry and the brain manufactures its own supply. Symptoms often attributed to monosodium glutamate have not been reproduced in blinded testing.
Why is it called non-essential?
Nutritionists divide amino acids into those the body cannot build, which must come from food, and those it can assemble for itself. Glutamic acid belongs to the second group, so no dietary requirement is set for it. The supplement sold as L-glutamic acid is the same molecule in the mirror image form the body uses.
Also known as
Used in a sentence
Glutamic acid at position six of the beta globin chain is replaced by valine in sickle cell disease.
Good to know
Glutamate swallowed in food behaves differently from glutamate released inside the brain, because the gut consumes most of it and the blood brain barrier limits what crosses, and blinded trials have not confirmed the symptoms commonly attributed to monosodium glutamate.
Word origin
Where “glutamic acid” comes from
From the Latin gluten, meaning glue, after the sticky wheat protein from which the acid was first isolated.