Glutamate isolation

In the 1950s, a group of coryneform bacteria which accumulate a large amount of L-glutamic acid in the culture medium were isolated (21). The use of mutant derivatives of these bacteria offered a new fermentation process for the production of many other kinds of amino acids (22). The amino acids which are produced by this method are mostiy of the T.-form, and the desired amino acid is singly accumulated. Therefore, it is very easy to isolate it from the culture broth. Rapid development of fermentative production and en2ymatic production have contributed to the lower costs of many protein amino acids and to their availabiUty in many fields as economical raw materials. 

Crotonoside. Crotonoside, also caHed isoguanosine, (45) has been isolated from Croton tiglium (4). Ip administration of [2- C]crotonoside to rats results in incorporation into nucleic acids (qv). It inhibits the inducible binding sites, inhibits glutamic acid dehydrogenase, and accumulates cAMP. 

Synaptic vesicles isolated from brain exhibit four distinct vesicular neurotransmitter transport activities one for monoamines, a second for acetylcholine, a third for the inhibitory neurotransmitters GABA and glycine, and a fourth for glutamate [1], Unlike Na+-dependent plasma membrane transporters, the vesicular activities couple to a proton electrochemical gradient (A. lh+) across the vesicle membrane generated by the vacuolar H+-ATPase ( vacuolar type proton translocating ATPase). Although all of the vesicular transport systems rely on ApH+, the relative dependence on the chemical and electrical components varies (Fig. 1). The... 

Lonart G, Johnson KM Inhibitory effects of nitric oxide on the uptake of [3H]dopamine and [3H]glutamate by striatal synaptosomes. J Neurochem 63 2108—2117, 1994 Lovinger DM, White G Ethanol potentiation of 5-hydroxytryptamine3 receptor-mediated ion current in neuroblastoma cells and isolated adult mammalian neurons. Mol Pharmacol 40 263—270, 1991... 

In subsequent experiments (66), this locked substrate was used to obtain evidence for the hypothesis (67) that enzyme-bound y-glutamyl phosphate 14 is an intermediate in the enzyme-catalyzed reaction. All attempts to isolate this acyl phosphate 14 have failed (66), presumably because of the marked tendency of this intermediate to cyclize to pyrrolidonecarboxyUc acid, 15, and to hydrolyze to glutamic acid. 

Nodularia spwnigena has also been shown to produce a peptide with hepato-toxic activity. The more recent reports come from Australia (76), the German Democratic Republic (77), Denmark (78), Sweden (79), and Finland (80,81). Recently structure information on Nodularia toxin has been presented by Rinehart (97) for waterbloom material collected in Lake Forsythe, New Zealand, in 1984 by Eriksson et al. (81) from waterbloom material collected in the Baltic Sea in 1986, and Runnegar et al. (82) for a field isolate from the Peel Inlet, Perth, Australia. Structure work by Rinehart, Eriksson, and Runnegar all indicate that the peptide is smaller than the heptapeptide toxins. Rinehart s work (97) indicates the toxin is a pentapeptide with a similar structure to the heptapeptides and containing fi-methylaspartic acid, glutamic acid, arginine, dehydrobutyrine, and ADDA (MW 824). 

Status epilepticus occurs because the brain fails to stop an isolated seizure. The exact reason for this failure is unknown and probably involves many mechanisms. A seizure is likely to occur due to a mismatch of excitatory and inhibitory neurotransmitters in the brain. The primary excitatory neurotransmitter in the brain is glutamate. Glutamate stimulates postsynaptic N-methyl-D-aspartate (NMDA) receptors in the brain, causing an influx of calcium into the cells and depolarization of the neuron. Sustained depolarization may maintain SE and eventually cause neuronal injury and death.7 The primary... 

In 1958 Barker (20) isolated a red, heat stable, light labile, cofactor which was required for the metabolism of glutamate in cell-extracts of Clostridium tetanomorphum. Subsequently this cofactor was crystallized. X-ray crystallography identified Barker s cofactor as the coenzyme form of Vitamin B12 (15, 21). 

Fig. 21.14. Isolated inside-out patch from pharyngeal muscle with a patch potential of +50 mV and 800 pM glutamate present in the patch pipette shows the opening of two Glu-CI channels. The addition of 1 pM ivermectin to the bath and thus to the inside of the patch produces (in the same patch) opening of up to three Glu-CI channels simultaneously. Ivermectin increases the probability of opening of Glu-CI channels already opening in the presence of glutamate.

Hundreds of different natural amino acids have been found and isolated. In some cases, they are quite complex and have a variety of functions. The preparation and isolation of amino acids occurs either from biological material or via chemical synthesis. Several amino acids, such as glutamic acid and methionine, are now prepared on a scale of 100,000 tons per year. 

A group at the Bach Institute in Moscow was able to isolate a flavine pigment (an isoalloxacine derivative) from the polymer obtained by heating a mixture of three amino acids (glutamic acid glycine lysine = 8 3 1) this exhibited photochemical acivity (e.g., redox reactions such as electron transfer to acceptors with lower Eo values) under both aerobic and anaerobic conditions (Kolesnikov and Kritsky, 1999). 

Crystallization remains the primary means of controlling the polymorphic or solva-tomorphic state of a compound, and various groups have examined the influences of processing parameters on the identity and quality of the isolated form. Seeding was used to reduce the size of the metastable zone of eflucimibe, and thereby control the identity of the desired polymorphic identity of the product through a reduction in concomitant crystallization [16], Process improvements have been developed that were found to improve the filterability and enhance the bulk density of ranitidine Form-1 [17], while the variation of process parameters used in an oscillatory baffled crystallizer enabled better selection to be made between the metastable a- and /i-forms of (z.)-glutamic acid [18]. 

Note that the strength of the correlations is increased by the fact that the citric acid pathway is today isolated in mitochondria derived from a distinct early life form and linked to both aspartate and glutamate, in which A and C are dominant amino-acid carriers, while glycolysis and the pentose shunt are cytoplasmic, where U and G are more dominant amino-acid carriers. 

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