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[Biochemistry](https://durgical.com/en/biochemistry/) · Topic

# Glucogenic and ketogenic amino acids

Depending on where its carbon skeleton ends up, an amino acid can be used to make glucose, ketone bodies or both.

Updated 2026-11-01

## Key facts

- Glucogenic: the skeleton gives pyruvate or Krebs cycle intermediates (α-ketoglutarate, succinyl-CoA, fumarate, oxaloacetate).
- Purely ketogenic: only leucine and lysine, which give acetyl-CoA or acetoacetyl-CoA.
- Both glucogenic and ketogenic: phenylalanine, tyrosine, tryptophan, isoleucine and threonine.
- Acetyl-CoA gives no net glucose, because pyruvate dehydrogenase is irreversible.

## In detail

- To pyruvate: alanine, serine, glycine, cysteine, threonine and tryptophan.
- To α-ketoglutarate: glutamate, glutamine, proline, arginine and histidine.
- To succinyl-CoA: valine, isoleucine, methionine and threonine, through propionyl-CoA and methylmalonyl-CoA (with biotin and B12).
- To fumarate: phenylalanine and tyrosine; to oxaloacetate: aspartate and asparagine.
- To acetyl-CoA or acetoacetyl-CoA: leucine, lysine, isoleucine, tryptophan, phenylalanine and tyrosine.
- In fasting, muscle releases mainly alanine and glutamine for gluconeogenesis in liver and kidney.

## Memory aid

Purely ketogenic: the two L's, Leucine and Lysine.

## Clinical notes

- In propionic and methylmalonic acidaemia, valine, isoleucine, methionine and threonine cannot enter the Krebs cycle.
- In maple syrup urine disease, leucine, which is purely ketogenic, is the most toxic.

## Related conditions

- [Propionic acidaemia](https://durgical.com/en/conditions/propionic-acidaemia/)
- [Methylmalonic acidaemia](https://durgical.com/en/conditions/methylmalonic-acidaemia/)
- [Maple syrup urine disease](https://durgical.com/en/conditions/maple-syrup-urine-disease/)
- [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/)

## Related

- [Krebs cycle (citric acid cycle)](https://durgical.com/en/biochemistry/pathways/krebs-cycle/)
- [Pyruvate](https://durgical.com/en/biochemistry/molecules/pyruvate/)
- [Acetyl-CoA](https://durgical.com/en/biochemistry/molecules/acetyl-coa/)
- [Alanine](https://durgical.com/en/biochemistry/molecules/alanine/)
- [Phenylalanine](https://durgical.com/en/biochemistry/molecules/phenylalanine/)
- [Tyrosine](https://durgical.com/en/biochemistry/molecules/tyrosine/)
- [Tryptophan](https://durgical.com/en/biochemistry/molecules/tryptophan/)
- [Branched-chain α-keto acid dehydrogenase (BCKDH)](https://durgical.com/en/biochemistry/enzymes/branched-chain-keto-acid-dehydrogenase/)
- [Transamination and deamination](https://durgical.com/en/biochemistry/topics/transamination-and-deamination/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which two amino acids are only ketogenic?

Leucine and lysine: their skeletons end as acetyl-CoA or acetoacetyl-CoA, which cannot give net glucose.

## Why can acetyl-CoA not make net glucose?

Pyruvate dehydrogenase is irreversible, and in the Krebs cycle the two acetyl carbons are lost as CO₂.

## Which amino acids enter the Krebs cycle as succinyl-CoA?

Valine, isoleucine, methionine and threonine, through propionyl-CoA and methylmalonyl-CoA.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Metabolism of amino acids and derivatives](https://reactome.org/PathwayBrowser/#/R-HSA-71291) (Reactome, 2026); [Branched-chain amino acid catabolism](https://reactome.org/PathwayBrowser/#/R-HSA-70895) (Reactome, 2026); [Propionyl-CoA catabolism](https://reactome.org/PathwayBrowser/#/R-HSA-71032) (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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Representative model, for educational purposes only.

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