Amino acids, glutamate

There are numerous transmitter substances. They include the amino acids glutamate, GABA and glycine acetylcholine the monoamines dopamine, noradrenaline and serotonin the neuropeptides ATP and NO. Many neurones use not a single transmitter but two or even more, a phenomenon called cotransmission. Chemical synaptic transmission hence is diversified. The basic steps, however, are similar across all neurones, irrespective of their transmitter, with the exception of NO transmitter production and vesicular storage transmitter release postsynaptic receptor activation and transmitter inactivation. Figure 1 shows an overview. Nitrergic transmission, i.e. transmission by NO, differs from transmission by other transmitters and is not covered in this essay. 

MSG is the sodium salt of the amino acid glutamic acid. It is made commercially by the fermentation of molasses, but exists in many products made from fermented proteins, such as soy sauce and hydrolyzed vegetable protein. 

FIGURE 19.18 Sickle-shaped red blood cells form when only one amino acid (glutamic acid) in a polypeptide chain is replaced by another amino acid (valine). These cells are less able to take up oxygen than normal cells. 

For example, the amino acid glutamine is synthesized in cells by the reaction of ammonia with another amino acid, glutamic acid ... 

The amino acid glutamate is the most widely used excitatory neurotransmitter in the central nervous system of mammals. Glutamate is the primary neurotransmitter used by the vast majority of reticular formation, thalamic and cortical neurons, which play a crucial role in the generation of the characteristic electrical activity as recorded in the electroencephalogram (for details see Steriade McCarley (2005)). The activity of these neurons is tightly regulated by the other neurotransmitters described in this chapter. 

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). 

THE AMINO ACID GLUTAMATE IS THE MAJOR EXCITATORY NEUROTRANSMITTER IN THE BRAIN 268... 

The method is limited in the scope as it has been successfully tried only in two amino acids, glutamic acid and aspartic acid. In others it has resulted only in partial resolution. Harada has now (1965) succeded in resolving free amino acids by inoculation. 

In the personal care market, fatty acid derivatives of proteins and amino acids (glutamic acid) are mainly used in mild shower and bath products, mild shampoos, surfactant-based face cleansers, cold-wave preparations and fixatives, baby wash formulations, as well as special emulsifiers for leave-on products. 

Several symport proteins have been identified in the luminal and basolateral surfaces of the proximal tubule cells, each with a specific transport function. For example, mechanisms exist for transport of (i) neutral amino acids, except glycine, (ii) glycine alone, (iii) acidic amino acids (glutamate and aspartate), (iv) basic amino acids... 

Amino Acids Glutamate NMDA, AMPA, kainate Cation conductance... 

Adenosine inhibits the evoked release of excitatory amino acids glutamate and aspartate (Poll et al. 

This enzyme is found in many tissues, where it catalyzes the reversible oxidative deamination of the amino acid glutamate. It produces the citric acid cycle intermediate a-ketoglutarate, which serves as an entry point to the cycle for a group of glucogenic amino adds. Its role in urea synthesis and nitrogen removal is stiU controversial, but has heen induded in Figure 1-17-1 and Table 1-17-1. 

There are, of course, several other theories as to how the atypical antipsychotics work. These focus on other neurotransmitters, including the neuropeptide neurotensin and the amino acid glutamate, and on a variety of other complex receptor activities. In the final analysis, we are still not sure just what makes the atypical antipsychotics work so well, but we are glad that they do. 

Amino acids and some small peptides are absorbed into the enterocytes in the jejnnnm. The transport of amino acids from the lumen into the ceU is an active process, coupled to the transport of Na ions down a concentration gradient. There are at least six carrier systems with different amino acid specificities neutral amino acids (i.e. those with no net charge, e.g. branched-chain amino acids) neutral plus basic amino acids imino acids (proline, hydroxyproline) and glycine basic amino acids (e.g. arginine and lysine) P-amino acids and taurine acidic amino acids (glutamic and aspartic acids). 

Figure 8.3 A summary of pathways involved in the synthesis of non-essential amino acids. Glutamate is produced from ammonia and oxoglutarate. Glutamate is the source of nitrogen for synthesis of most of the amino acids. Cysteine and tyrosine are different because they require the essential amino acids (methionine and phenylyalanine) for their synthesis. These two amino acids are, therefore, conditionally essential, i.e. when there is not sufficient methionine or phenylyalanine for their synthesis, they are essential (Details are in Appendix 8.2).

The amino acid glutamate is deaminated in a reaction catalysed by the enzyme glutamate dehydrogenase, using either NAD+ or NADF as the oxidising agent, as follows ... 

Three amino acids, glutamate, aspartate and glycine, are neurotransmitters. 

The concentration of anunonia refers to the total anunonia, that is NH3 plus NH4L For comparison, the concentration of ATP in the cell is 10 nunol/L, that of glucose 6-phosphate is 0.5 nunol/L and that of the amino acid glutamate in plasma is 0.02 nunol/L. 

Vitamin K is a component of the carboxylase enzyme that carboxylates the amino acid glutamate in proteins to form y-carboxyglutamate, which binds calcium ions i.e. it catalyses a post-transcriptional modification. Proteins so carboxylated include clotting factors (Factors 11, Vll, IX, and X) and two proteins in bone oesteocalcin (known as matrix-gln-protein) and bone gin protein (BGP). The... 

The mechanism of action of warfarin becomes apparent from the molecular details of the blood clotting process. The clotting factors VII, IX, and X require Ca ions for maximum activity. These proteins possess a novel amino acid which binds Ca ions. It is a modified form of the amino acid glutamate, as y-carboxyglutamate (Gla) which possesses two... 

There is now evidence that the mammalian central nervous system contains several dozen neurotransmitters such as acetylcholine, noradrenaline, dopamine and 5-hydroxytryptamine (5-HT), together with many more co-transmitters, which are mainly small peptides such as met-enkephalin and neuromodulators such as the prostaglandins. It is well established that any one nerve cell may be influenced by more than one of these transmitters at any time. If, for example, the inhibitory amino acids (GABA or glycine) activate a cell membrane then the activity of the membrane will be depressed, whereas if the excitatory amino acid glutamate activates the nerve membrane, activity will be increased. The final response of the nerve cell that receives all this information will thus depend on the balance between the various stimuli that impinge upon it. 

The proteinogenic amino acid glutamate (Glu) and the biogenic amine 4-aminobuty-rate derived from it are among the most important neurotransmitters in the brain (see p. 352). They are both synthesized in the brain itself In addition to the neurons, which use Glu or GABA as transmitters, neuroglia are also involved in the metabolism of these substances. 

Pharmacology Persistent activation of CNS N-methyl-D-aspartate (NMDA) receptors by the excitatory amino acid glutamate has been hypothesized to contribute to the symptomatology of Alzheimer disease. Memantine is an NMDA receptor antagonist. 

The amino acids of primary interest to the pharmacologist fall into two categories the acidic amino acid glutamate and the neutral amino acids glycine and GABA. All these compounds are present in high concentrations in the CNS and are extremely potent modifiers of neuronal excitability. 

Domoic acid, known as an excitotoxin, acts as an analogue of the amino acid glutamate, incorporating a similar structure. It is believed to bind at the same site on the "kainate receptor."... 

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