14. Synthesis of non-essential amino acids

Last updated on January 11, 2020 at 13:12


  • The synthesis of non-essential amino acids is regulated by negative feedback of the different amino acids
  • You should know the MRTs related to this
  • Converting nitrogen gas (N2) to ammonia in a very energetically expensive process
  • In humans, ammonia is incorporated into organic compounds by the glutamine synthetase reaction
  • Alanine, aspartate, asparagine, glutamine and serine are the non-essential amino acids
  • Proline, arginine, glycine, cysteine, glutamine and tyrosine are the conditionally essential amino acids, which means that they can be synthesized, but not always in sufficient amounts


The bond between nitrogen atoms in N2 gas is very strong. That means that it requires a lot of energy to break. In biological systems, it needs 16 ATP and 8 electrons.

In humans, the most important reaction for incorporating ammonia into organic molecules is the glutamine synthetase, which incorporates ammonia in glutamate to give glutamine.


Proline is a special amino acid in that it exists in both trans and cis conformations, unlike other amino acids. Proline residues are found in collagen and HIF-1α, for example (as they’re hydroxylated by proline hydroxylase).

Biosynthesis of amino acids

There are many MRTs related to this. You should know that there are three major types of reactions used in this synthesis. With important cofactors in parenthesis, they are aminotransferases (PLP), amidotransferases and one-carbon group transfer reactions (biotin, THF, adoMet).

PRPP (phosphoribosyl pyrophosphate) is an important molecule in the biosynthesis of histidine, tryptophan and nucleotides. The synthesis of PRPP is an MRT.

Regarding the regulation, each pathway contains a negative feedback mechanism, where the amino acid product inhibits the first enzyme in the pathway.

Learn this if you’re going for the gyulla prize or what it’s called. If you’re going for 2, don’t waste time on this.

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13. Amino acid metabolism; the fate of the carbon skeleton

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15. Enzymopathies of amino acid metabolism

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