Glutamate decarboxylase, histamine

Acetylcholine is formed from choline (which is also an important constituent of phospholipids) and acetyl CoA under the catalytic influence of choline acetyl-ase. It is hydrolised by acetylcholinesterase or choline esterase. Two important steps in the formation of noradrenaline from tyr dopa decarboxylase and dopamine hydroxylase. Adrenaline is formed from noradrenaline by phenyl ethanolamine A -methyltransferase. Both noradrenaline and adrenaline are metabolised by catechol 0-methyl transferase or monoamine oxidase. Some later steps in their metabolism involve aldehyde dehydrogenase and alcohol dehydrogenase (aldehyde reductase), After hydroxylation to its 5-hydroxy derivative, tryptophan is converted by 5-hydroxytryptophan decarboxylase to 5-hydroxytryptamine (serotonin). The major routes of serotonin metabolism involve either monoamine oxidase or hydroxyindole 0-methyltransferase. Histamine is synthesised from histidine by histidine decarboxylase, and is metabolised by either diamine oxidase or histamine Af-methyltransferase. Gamma aminobutyric acid is formed by glutamate decarboxylase and metabolised by... 

SNA does not affect the concentrations of histamine and glutamic add, but It decreases the activity of glutamic acid decarboxylase and reduces the concentrations of gamma-aminobutyric acid (GABA) In rat brain. 5 GABA release Is Inhibited by acute administration, but not by chronic treatment. 5 SNA Increases serum creatinine phosphoklnase content In stressed rats. Recently, SNA was found to decrease methionine-enkephalin content In the medulla oblongata and mldbraln In the mouse, whereas other areas remained unaffected.48... 

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