Glutamate 5-semialdehyde

Figure 33. Synthesis of alkaloids from ornithine. Aikaioids are derived via putrescine or glutamic semialdehyde. At least two enzymes, ODL (Ornithine decarboxylase) or PDL (Pyrroline...

Is in equilibrium with its open form, a-glutamic semialdehyde... 

Ornithine is required to maintain the urea cycle. Conversion of glutamate to ornithine via glutamate semialdehyde is therefore an anaplerotic reaction. Melatonin is a compound synthesized from serotonin. It has a function in the circadian rhythm activity and has nothing to do with intracellular protein degradation. 

Oxidation of proline and arginine residues leads also to formation of glutamate semialdehyde and, upon its further oxidation, to pyroglutamic acid (A9). Oxidized proline produces also 2-pyrrolidone (K6) (Fig. 5). 

Proline and arginine can be derived from glutamate semialdehyde, which is formed by reduction of glutamate. 

Arginine, via three reactions of the urea cycle, can be derived from ornithine, which is produced by transamination of glutamate semialdehyde. 

Arginine can be cleaved by arginase in the liver to form urea and ornithine. Ornithine can be transaminated to glutamate semialdehyde, which can be oxidized to glutamate. 

The cofactor required for the reaction that produces ornithine from glutamate semialdehyde is... 

B. Glutamate semialdehyde is transaminated to form ornithine. Glutamate provides the... 

Scheme 11 Oxidation of proline causes ring opening with the resultant formation of glutamic semialdehyde...

The major pathway for catabolism of arginine is arginase to form ornithine, followed by ornithine transamination and oxidation of the resulting glutamic semialdehyde to form glutamate. For the most part, this catabolism occurs... 

The glutamic semialdehyde formed in the intestine can also cyclize and be reduced to form proline. Therefore, proline is not an essential amino acid in people. Any amino acid that can form glutamate can be converted to glucose. Among the amino acids that can produce glutamate, which will be examined in more detail when they are discussed individually, are glutamine, arginine via ornithine formation, proline, and histidine. 

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