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.

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.

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

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.

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.

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

Sources: Metabolism of amino acids and derivatives (Reactome, 2026); Branched-chain amino acid catabolism (Reactome, 2026); Propionyl-CoA catabolism (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.