Glutamic Acid
Properties
| State | Solid (white crystalline powder) |
| Color | White |
| Solubility | Slightly soluble in water (8.6 g/L at 25°C); soluble in hot water and dilute acids |
| Melting Point | 199°C (decomposes) |
| Boiling Point | Decomposes before boiling |
About Glutamic Acid
Glutamic acid is a five-carbon dicarboxylic amino acid — alpha-amino at C2, alpha-carboxyl at C1, and a side-chain gamma-carboxyl at C5 — with a molar mass of 147.129 g/mol and three ionizable groups (pKa1 ≈ 2.19 for alpha-COOH, pKa2 ≈ 9.67 for alpha-NH3+, pKa3 ≈ 4.25 for the gamma-COOH). At physiological pH the side chain sits as carboxylate, making the predominant species the singly-negative glutamate anion that the literature usually just calls glutamate. The chemistry that makes glutamate biologically central is straightforward: its alpha-keto analogue is alpha-ketoglutarate, a TCA-cycle intermediate, so transamination between glutamate and any other alpha-keto acid is a one-enzyme step (catalyzed by aminotransferases using PLP as cofactor). That reaction collects amino groups from dietary protein into a single nitrogen pool that glutamate dehydrogenase can then deaminate into NH4+ for the urea cycle. In the brain, glutamate is the dominant fast excitatory neurotransmitter at roughly 90% of CNS synapses, signaling through ionotropic AMPA, NMDA, and kainate receptors plus eight metabotropic mGluR subtypes — and excessive glutamate release drives the excitotoxic neuronal death that kills tissue around an ischemic stroke core. Industrially, around 3 million tonnes of MSG (the monosodium salt) get produced annually by Corynebacterium glutamicum fermentation of glucose or molasses; the bacterium oversecretes glutamate when its biotin nutrition is starved enough to weaken the cell membrane.
Where you'll encounter it
If you've ever tasted a parmesan rind, a soy-sauce-soaked steak, or a long-simmered tomato sauce, you've experienced glutamate's umami signal at TAS1R1/TAS1R3 receptors on your tongue — and 'aged' or 'fermented' foods taste savory specifically because protein hydrolysis liberates free glutamate from polypeptides. A 36-month aged Parmigiano-Reggiano contains roughly 1.2 g of free glutamate per 100 g, which is why even a small grating delivers a savory punch that fresh mozzarella (essentially zero free glutamate) cannot match. A neuroscientist patch-clamping a hippocampal slice puffs 100 µM glutamate onto a CA1 pyramidal cell to drive NMDA-receptor calcium influx and trigger LTP — the same Ca2+ entry that encodes memory becomes the lethal excitotoxic signal in an ischemic stroke core. Fermentation engineers run Corynebacterium glutamicum on biotin-limited glucose feed to weaken the membrane and trigger glutamate oversecretion at industrial scale.
Common Uses
- Fermentation product as monosodium glutamate (MSG) flavor enhancer
- Hub amino acid for transamination via glutamate-dehydrogenase chemistry
- Precursor in biosynthesis of glutamine, GABA, glutathione, and proline
- Buffering agent in chromatography and protein crystallization screens
- Substrate in ion-exchange resin manufacture (poly-glutamate hydrogels)
- Component of amino acid IV nutrition formulations
- Tracer molecule in glutamatergic neurotransmission research
Safety Information
GRAS classification for both glutamic acid and MSG; oral LD50 in rats is 19.9 g/kg for MSG. JECFA removed the previous Acceptable Daily Intake limit in 1987 after concluding intake at any normal dietary level is safe. The 'Chinese Restaurant Syndrome' claim from the 1960s never reproduced under double-blind testing. Real concerns: people on severely sodium-restricted diets should track MSG (it's about 12% sodium by mass, vs. 39% for NaCl), and intracerebroventricular glutamate injection in neonatal rodents causes hypothalamic damage — but this requires bypassing the blood-brain barrier and has no dietary equivalent. No GHS hazard classification.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.