1. Amino acid biosynthesis
Chemistry 256

2. 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.

3. Some non-essential amino acid syntheses are straightforward
These have been seen else-where in the text.

4. Others less so...

5. Especially the aromatic ones!

6. A study in regulation: Glutamine synthetase
D6 symmetry; mammalian glutamine synthetase is controlled by α-ketoglutarate to prevent ammonia accumulation.

7. 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.

8. Woolfolk C. A. , Stadtman E. R
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).

9. 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.

10. Westley, J. , and Ceithaml, J
Westley, J., and Ceithaml, J., “Synthesis of Histidine in Escherichia Coli”, Arch. Biochem. And Biophys. (1955)

11. 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)

12. Heme is degraded and excreted

13. A variety of neurotransmitters and hormones are synthesized from amino acids

14. Nitrogen fixation by some bacteria (diazotrophs) requires nitrogenase
Yes, molybdenum is a nutrient!
(for these bacteria, anyway)