Glutamic acid

Ball-and-stick Stick Space-filling

Drag to rotate; pinch or Ctrl + scroll to zoom. Arrow keys rotate, + − zoom, R resets.

19 atoms, 18 bonds.

IUPAC name: (2S)-2-aminopentanedioic acid
Molar mass: 147.130(17) g/mol
Atoms: 19
SMILES: C(CC(=O)O)C(C(=O)O)N
InChIKey: WHUUTDBJXJRKMK-VKHMYHEASA-N
PubChem CID: 33032

Made of

Structural formula of glutamic acid. Each unlabelled corner is a carbon atom, and the five hydrogens on carbon are not drawn. Wedges come toward you, hashes go back. It shows which atoms are joined to which, not the shape. The model above shows the shape.

A carboxyl group, –COOH, caps each end of a chain of five carbon atoms, and the second carbon also carries an amino group, –NH₂. The IUPAC name, (2S)-2-aminopentanedioic acid, spells out exactly that arrangement. ChEBI, the Chemical Entities of Biological Interest database, classes this L form as a proteinogenic amino acid, one that cells build into proteins. It lists D-glutamic acid as its mirror-image form, or enantiomer.

Hydrogen, nitrogen and oxygen complete the formula, C₅H₉NO₄, which weighs in at 147.13 g/mol. The solid forms white crystals or a crystalline powder, odourless according to the Hazardous Substances Data Bank (HSDB). Only 8.57 g dissolves in a litre of water at 25 °C on HSDB’s figure, and practically none in ethanol or ether. The solution turns acidic, near pH 2 in HSDB’s data and 3.0 to 3.5 when saturated under European Union food-additive rules.

Structure and bonding

The model holds 19 atoms and 18 bonds and no ring: its five carbons run as one open chain. With Labels on, the four O symbols sit in pairs on the two end carbons, and the single N on the carbon beside one end. In Ball-and-stick and Stick, each end carbon has three partners: the chain, a double-bonded oxygen, and a single-bonded oxygen capped with hydrogen. The three middle carbons carry four single bonds each, the tetrahedral arrangement Chem1 gives carbon in most of its organic compounds. Space-filling merges everything into one outline, red oxygen at both ends.

The second carbon, bonded to the amino group, a hydrogen and both arms of the chain, is the stereocentre whose arrangement the (2S) of the name records. The model draws the neutral molecule, yet in water glutamic acid gives up protons. In each acid group, the hydrogen’s acidity comes almost entirely from the doubly bonded oxygen pulling electrons away, on Chem1’s account. How amino acids carry charge in water is set out for glycine.

Where it turns up

In wheat, glutamic acid accounts for 40 per cent of the gliadin in gluten, HSDB reports. Human milk also carries it as a free amino acid, one not bound into protein. With taurine it leads the free amino acids of the earliest milk, according to HSDB, and it rises about two and a half times as lactation goes on. Farther afield, NASA scientists found aspartic and glutamic acids among the primordial molecules of the meteorite Asuka 12236.

Industry first took it from vegetable proteins split with hydrochloric acid, isolating L-glutamic acid hydrochloride, HSDB records. Direct fermentation followed in 1956, and a synthesis from acrylonitrile ran from 1962 to 1973. Fermentation lowered costs and environmental load so far that every glutamate maker switched to it. In the US it now holds registrations as a crop growth enhancer, and HSDB lists it as a raw material for peptide drugs.

Why it matters

Under the name glutamate, it is an excitatory neurotransmitter of the central nervous system, the brain and spinal cord: a chemical messenger that drives nerve cells to fire. MeSH, the Medical Subject Headings thesaurus, calls it the most common one there. In the mammalian cortex, HSDB records, glutamate is the main excitatory neurotransmitter and GABA, gamma-aminobutyric acid, the main inhibitory one. Glutamic acid is GABA’s precursor too, through the enzyme glutamic acid decarboxylase.

NMDA receptors are channels on nerve cells; in those built with a GluN2A subunit, glutamate binds to that subunit. When glutamate and glycine attach, the channel opens and cations, positively charged ions, flow through. Their current excites the neuron to send a signal on. MedlinePlus ties these receptors to brain development, to the brain’s changes with experience, and to learning and memory.

Sight in dim light runs on glutamate as well. Rod cells, the retina’s low-light sensors, release it onto bipolar cells, where it binds a receptor called mGluR6. That binding sets the bipolar cells passing the visual signal on toward the brain.

Properties

Properties of glutamic acid Molar mass summed from IUPAC/CIAAW 2024 standard atomic weights; formula, atom and bond counts and PubChem's molecular weight from PubChem CID 33032.
Property	Value	Unit	Source
Molecular formula (Hill order)	C₅H₉NO₄
Molar mass	147.130(17) g/mol	g/mol	IUPAC/CIAAW 2024
Carbon atoms	5
Hydrogen atoms	9
Nitrogen atoms	1
Oxygen atoms	4
Bonds	18
Single bonds	16
Double bonds	2
PubChem molecular weight	147.13 g/mol	g/mol	PubChem

Safety

As food protein or a food ingredient, glutamic acid is essentially harmless; US rules class it as generally recognised as safe when it serves as a salt substitute. Of 307 company reports to the European Chemicals Agency, 293 (95.4%) find it meets no hazard criterion of the Globally Harmonized System (GHS). HSDB classifies it with the signal word Danger, for severe skin burns and eye damage. The PubChem Laboratory Chemical Safety Summary for glutamic acid holds both the majority finding and HSDB’s classification.

Questions

What does glutamic acid do outside the brain?

The Hazardous Substances Data Bank (HSDB) calls glutamate a central junction where amino nitrogen changes hands, helping cells both build and break down amino acids. In the liver, ammonia leaves amino acids by way of glutamate, and the glutamate level there adjusts how fast that ammonia is detoxified. In the pancreas, beta-cells oxidise glutamate as one step in the insulin release that amino acids trigger.

Is glutamic acid the same as glutamate?

Not quite. Glutamic acid is the neutral acid the model draws, and glutamate is what remains once it gives up a proton. ChEBI names that ion L-glutamate(1−) and calls glutamic acid its conjugate acid. It can lose more than one proton: the Hazardous Substances Data Bank (HSDB) gives it three pK values, 2.19, 4.25 and 9.67. In the nervous system the messenger goes by glutamate.

What does glutamic acid have to do with sickle cell disease?

In sickle cell disease, valine takes the place of glutamic acid at position 6 of beta-globin, one of the protein subunits of haemoglobin, a change written Glu6Val. MedlinePlus explains that the altered haemoglobin S subunits then cling to one another in long, rigid molecules, which bend red cells into a sickle or crescent shape. Those cells die early, which can leave too few red cells (anaemia). In haemoglobin C, lysine replaces glutamic acid at the same position.

Can too much glutamate harm nerve cells?

An excess can kill or damage neurons, according to the National Institute of Neurological Disorders and Stroke. The institute links it to Parkinson's disease, stroke, seizures and heightened sensitivity to pain. Transporters such as EAAT1 clear surplus glutamate from the spaces between cells, since a buildup there would poison neurons. Glutamate also has a part in epilepsy, schizophrenia, depression, alcoholism and Alzheimer's disease, according to the National Institute of Mental Health.

Made of the same elements

C₈H₉NO₂ Acetaminophen 20 atoms, 20 bonds.
C₃H₇NO₂ Alanine 13 atoms, 12 bonds.
C₅H₆N₂O₂ Thymine 15 atoms, 15 bonds.
C₈H₁₁NO₂ Dopamine 22 atoms, 22 bonds.
C₆H₁₃NO₂ Isoleucine 22 atoms, 21 bonds.
C₆H₁₃NO₂ Leucine 22 atoms, 21 bonds.
C₉H₁₁NO₃ Tyrosine 24 atoms, 24 bonds.
C₉H₁₁NO₂ Phenylalanine 23 atoms, 23 bonds.

All 25 compounds made of carbon, hydrogen, nitrogen and oxygen

C₈H₁₀N₄O₂ Caffeine 24 atoms, 25 bonds.
C₉H₁₃NO₃ Epinephrine 26 atoms, 26 bonds.
C₂H₅NO₂ Glycine 10 atoms, 9 bonds.
C₄H₄N₂O₂ Uracil 12 atoms, 12 bonds.
C₅H₄N₄O₃ Uric acid 16 atoms, 17 bonds.
C₄H₅N₃O Cytosine 13 atoms, 13 bonds.
C₅H₅N₅O Guanine 16 atoms, 17 bonds.
C₁₀H₁₂N₂O Serotonin 25 atoms, 26 bonds.
C₁₁H₁₂N₂O₂ Tryptophan 27 atoms, 28 bonds.
CO(NH₂)₂ Urea 8 atoms, 7 bonds.
C₁₂H₁₇NO DEET 31 atoms, 31 bonds.
C₁₃H₁₆N₂O₂ Melatonin 33 atoms, 34 bonds.
C₁₄H₁₈N₂O₅ Aspartame 39 atoms, 39 bonds.
C₁₃H₂₁NO₃ Albuterol 38 atoms, 38 bonds.
C₁₄H₂₂N₂O Lidocaine 39 atoms, 39 bonds.
C₁₇H₂₁NO Diphenhydramine 40 atoms, 41 bonds.
C₂₀H₂₄N₂O₂ Quinine 48 atoms, 51 bonds.