Description
L-Glutamic acid, or L-2-aminopentanedioic acid, is a naturally
occurring amino acid of plant and animal proteins. It has a very
faint odor reminiscent of yeast or freshly baked bread. It has a
mild, somewhat sweet, meat-like taste.
The average glutamic acid content of food proteins is 20 percent.
Expressed as glutamic acid per 100 g of the edible portions,
medium fat beef contains about 2.65 g of glutamic acid; whole
liquid cow milk, 0.82 g; lean pork, 2.16 g; haddock, 2.32 g; peas,
5.58 g; soybeans, 7.01 g; commeal, 1.62 g; and whole grain wheat
flour, 4.16 g. In addition, free glutamic acid is present in many
vegetables, fish, and meats in small amounts (0. 005 to 0.23 g per
100 g) and as high as 2 g per 100 g in some varieties of cheese.
Recent estimates of free amino acids in the milk of various species
indicated that the free glutamic acid in human milk is about 0.22
g per 100 mL.
Glutamic acid and its salts are prepared commercially by hydrolysis
of gluten (wheat, corn, soybean, sugarbeet protein); by fermentation
from glucose-containing raw materials; the racemic acid
may be resolved into the d- and ι-isomer by fractional crystallization;
from 2 -cyclopentenylamine; by microbial conversion of aketoglutaric
acid; or by an alternative method, using Bacillus
megatherium-cereus; from fumaric acid using B. pumilus; from
starch.
Glutamic acid and the hydrochloride as well as the mono-sodium,
-potassium, and -ammonium salts of L-glutamic acid share similar
physical properties: they are nearly odorless, white, free-flowing
crystalline powders, and except for glutamic acid and glutamic
acid hydrochloride, are freely soluble in water. Glutamic acid is
slightly soluble and glutamic acid hydrochloride moderately soluble
in water. The pH of a saturated solution is about 3.2.
Occurrence
Reported as occurring in many vegetable proteins, in beef fbrin, in the chrysalis of silkworm, in the hydro- lysate of crystalline insulin Also present in other important peptides, such as glutathione, tyrocidin, folic acid, β-lactoglobulin, secretin and bacitracin, and in growth hormone
Definition
ChEBI: An optically active form of glutamic acid having L-configuration.
Preparation
By hydrolysis of gluten (wheat, corn or other vegetable sources); by fermentation from glucose-containing raw materials; the racemic acid may be resolved into the d- and l-isomer by fractional crystallization; from 2-cyclopentenylamine; by microbial conversion of α-ketoglutaric acid; or by an alternative method, using Bacillus megatherium-cereus; from fumaric acid, using B pumilus; from starch.
Biotechnological Production
For industrial production of L-glutamic acid, molasses (sucrose), starch hydrolysates (glucose) and ammonium sulfate are generally used as carbon and nitrogen sources, respectively. Key factors in controlling the fermentation are the presence of biotin in optimal concentration – to optimize cell growth and the excretion of Lglutamate – and sufficient supply of oxygen to reduce the accumulation of byproducts, such as lactic and succinic acid. In biotin-rich fermentation media the addition of penicillin or cephalosporin C favors the overproduction of L-glutamic acid due to effects on the cell membrane. The supplementation of fatty acids also results in an increased permeability of the cells thus enhancing glutamate excretion.
A strain of Microbacterium ammoniaphilum cultured under biotin-deficient conditions produced 58 % of L-glutamic acid formed from glucose via phosphoenolpyruvate, citrate, and of a-ketoglutarate and the other 42 % via the tricarboxylic acid (TCA) or the glyoxylate cycle.
General Description
This certified reference material (CRM) is produced and certified in accordance with ISO/IEC 17025 and ISO 17034. This CRM is traceable to primary material from an NMI, e.g. NIST or NMIJ.
Certified content by quantitative NMR incl. uncertainty and expiry date are given on the certificate.
Download your certificate at: http://www.sigma-aldrich.com.
Biological Activity
The predominant excitatory transmitter in the mammalian central nervous system. Acts at ionotropic and metabotropic glutamate receptors.
Biochem/physiol Actions
L-Glutamic acid along with l-Lysine is used for preparation of bifunctional DTPA-like ligands. L-glutamic acid can stimulate the spontaneous release of [3H] dopamine ( [3H] DA).
Purification Methods
Crystallise L-glutamic acid from H2O acidified to pH 3.2 by adding 4volumes of EtOH, and drying at 110o. Likely impurities are aspartic acid and cysteine. It sublimes at 170-175o/10mm. It melts at 160o with cyclisation to L-pyrrolidone carboxylic acid. [Dunn & Brophy J Biol Chem 99 224 1958, Parikh et al. J Am Chem Soc 80 9571958, Greenstein & Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 pp 1929-1952 1961, Beilstein 4 III 1530, 4 IV 3028.]