Amino acid biosynthesis Chemistry 256. Why biosynthesis? So that every amino acid is not an...
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Transcript of Amino acid biosynthesis Chemistry 256. Why biosynthesis? So that every amino acid is not an...
![Page 1: Amino acid biosynthesis Chemistry 256. Why biosynthesis? So that every amino acid is not an essential one. In other words, humans do not have to consume.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f2c5503460f94c473d8/html5/thumbnails/1.jpg)
Amino acid biosynthesis
Chemistry 256
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Why biosynthesis?
• So that every amino acid is not an essential one. In other words, humans do not have to consume a non-essential amino acid in order to have it for use in the cells.
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Some non-essential amino acid syntheses are straightforward
• These have been seen else-where in the text.
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Others less so...
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Especially the aromatic ones!
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A study in regulation: Glutamine synthetase
• D6 symmetry; mammalian glutamine synthetase is controlled by α-ketoglutarate to prevent ammonia accumulation.
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Bacterial glutamine synthetase regulation• Much more complex; requires adenylylation, which is
the addition of an AMP to key tyrosine residues.• The enzyme adenylyltransferase is activated by
uridylylation, the addition of a UMP, a reaction catalyzed by uridylyltransferase.
• So, if there is high [α-ketoglutarate], this triggers uridylylation of adenylyltransferase, which activates it to adenylylate glutamine synthetase, which activates that to produce more glutamine.
• Not a digital system: different levels of uridylylation and adenylylation lead to different rates.
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Woolfolk C. A., Stadtman E. R. , “Cumulative feedback inhibition in the multiple end-product regulation of glutamine synthetase activity in Escherichia coli”, Biochem. Biophys. Res. Commun. (1964).
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Some amino acid syntheses are complex
• Glutamate leads to proline, ornithine, arginine (several steps)
• 3-phosphoglycerate (3PG) leads to serine, cysteine, glycine (several steps)
• Plants and microorganisms synthesize aspartate into lysine, methionine and threonine; pyruvate into leucine, isoleucine and valine; and so forth.
• The synthesis of histidine in plants is similar to the synthesis of nucleotides.
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Westley, J., and Ceithaml, J., “Synthesis of Histidine in Escherichia Coli”, Arch. Biochem. And Biophys. (1955)
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Heme is synthesized from glycine and succinyl-CoA
• Shemin, D., London, I.M., Rittenberg, D., “The in vitro synthesis of heme from glycine by nucleated red blood cells”, J Biol Chem (1948)
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Heme is degraded and excreted
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A variety of neurotransmitters and hormones are synthesized from amino acids
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Nitrogen fixation by some bacteria (diazotrophs) requires nitrogenase
Yes, molybdenum is a nutrient!(for these bacteria, anyway)