Amino acid metabolism
| Parent |
| Carboxylic acid metabolism Nitrogen metabolism Amine metabolism |
| Subordinate |
| Sulphurous A. Glutamine Family-A. Aspartate family-A. Serine family-A. Aromatic A. Histidine Family-A. non-proteinogenic A. D-amino acids |
| Gene Ontology |
|---|
| QuickGO |
As amino acid metabolism the totality of all biochemical processes is known that in a living being to build up or breakdown of amino acids lead.
| amino acid | Ketogenic Products | Glucogenic Products |
|---|---|---|
| Alanine | Pyruvate | |
| Glycine → serine | Pyruvate | |
| Threonine | acetate | Pyruvate, succinyl-CoA |
| Cysteine | Pyruvate | |
| Asparagine → aspartate | Oxaloacetate / fumarate | |
| Glutamine → glutamate | α-ketoglutarate | |
| Proline → glutamate | α-ketoglutarate | |
| Arginine → glutamate | α-ketoglutarate | |
| Histidine → glutamate | α-ketoglutarate | |
| Methionine | Succinyl-CoA | |
| Lysine | Acetyl-CoA | |
| Phenylalanine → tyrosine | Acetoacetate | Fumarate |
| Tryptophan | Acetyl-CoA | Pyruvate |
| Valine | Succinyl-CoA | |
| Leucine | Acetoacetate, acetyl-CoA | |
| Isoleucine | Acetyl-CoA | Succinyl-CoA |
Biosynthesis of proteinogenic L amino acids
Alanine is formed from pyruvate. Glycine and serine can be synthesized from 3-phosphoglycerate , an intermediate in glycolysis . Glutamate is formed from α-ketoglutarate ( citric acid cycle ). Proline, arginine and glutamine can then be produced from glutamate. Aspartate and asparagine can be made from oxaloacetate (citric acid cycle). Cysteine is formed when the sulfur-containing essential amino acid methionine is broken down. Tyrosine is generated from the essential amino acid phenylalanine. Essential amino acids cannot be formed by the human body because their synthesis is relatively laborious and the enzymes necessary for them have been lost in the course of evolution . This applies, for example, to the aromatic amino acids phenylalanine and tryptophan as well as to the branched amino acids valine, leucine and isoleucine.
Breakdown of proteinogenic L- amino acids
The proteinogenic amino acids are broken down in a variety of ways. They can be broken down into precursors for gluconeogenesis and are therefore glucogenic. If they are broken down to precursors of ketone synthesis , they are ketogenic. In most cases, the amino acid breakdown begins with the splitting off of the amino group by deamination . The nitrogen is introduced into the urea cycle via glutamate and aspartate and excreted in mammals as urea via the kidneys. In addition, excretion via uric acid or ammonium ions is common in many animal species .
Congenital amino acid degradation defects
almost all of them are inherited as an autosomal recessive trait and, if left untreated, usually lead to severe and irreversible damage to the CNS . The most common forms are:
- Phenylketonuria , PKU , syn .: Fölling's disease , the tyrosine metabolism is disturbed
- Albinism , the tyrosine or doping metabolism is only disturbed in the melanocytes; it would be fatal across the body
- Alkaptonuria , the tyrosine metabolism disrupted
- Maple syrup disease syn .: ketoaciduria , leucine , isoleucine and valine metabolism are disturbed
Metabolic pathways
literature
- JM Berg, JL Tymoczko, L. Stryer: Biochemistry. 6th edition. Spectrum Academic Publishing House, Elsevier GmbH, Munich 2007; ISBN 978-3-8274-1800-5 ; Chapters 23 and 24
