Glutamate action

An estimation of the amount of amino acid production and the production methods are shown ia Table 11. About 340,000 t/yr of L-glutamic acid, principally as its monosodium salt, are manufactured ia the world, about 85% ia the Asian area. The demand for DL-methionine and L-lysiae as feed supplements varies considerably depending on such factors as the soybean harvest ia the United States and the anchovy catch ia Pern. Because of the actions of D-amiao acid oxidase and i.-amino acid transamiaase ia the animal body (156), the D-form of methionine is as equally nutritive as the L-form, so that DL-methionine which is iaexpensively produced by chemical synthesis is primarily used as a feed supplement. In the United States the methionine hydroxy analogue is partially used ia place of methionine. The consumption of L-lysiae has iacreased ia recent years. The world consumption tripled from 35,000 t ia 1982 to 100,000 t ia 1987 (214). Current world consumption of L-tryptophan and i.-threonine are several tens to hundreds of tons. The demand for L-phenylalanine as the raw material for the synthesis of aspartame has been increasing markedly. 

It has a molecular weight of about 34000 and contains one Zn tetrahedrally coordinated to two histidine N atoms, a carboxyl O of a glutamate residue, and a water molecule. The precise mechanism of its action is not finally settled in spite of the intensive study of model systems, but it is agreed that the first step is coordination of... 

Most neurons in the central nervous system are stimulated by L- glutamate, the major excitatory amino acid in the brain. The postsynaptic actions of... 

Other systems also interact with glutamate. Activation of L-type voltagegated calcium channels (VGCC) occurs with NMDA receptor activation. Lamotrigine blocks several ion channels, including P- and N-type VGCC channels, an action that blocks the euphoric effects of ketamine and reduces dysphoric and cognitive effects (Hundt et al. 1998). Other modulatory sites,... 

Turning now to chemical attack, many predators immobilize their prey by injecting toxins, often neurotoxins, into them. Examples include venomous snakes, spiders, and scorpions. Some spider toxins (Quick and Usherwood 1990 Figure 1.3) are neurotoxic through antagonistic action upon glutamate receptors. The venom of some scorpions contains polypeptide neurotoxins that bind to the sodium channel. 

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