Alanine: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Alanine: which stations follow one another, which enzymes carry out each step and which cofactors they use. Every statement has a source. The page describes general textbook knowledge and says nothing about any individual person.

In brief

Alanine is an amino acid the body can build itself. Muscle forms it from pyruvate and an amino group and sends it to the liver, which turns it back into glucose and urea.

The pathway step by step

1. Glucose → Pyruvate Glycolysis · NAD⁺ In glycolysis, glucose is broken down to pyruvate in several steps. The cell gains ATP in the process. Source 4
2. Pyruvate → Alanine ALT · Vitamin B6 (PLP), Glutamate Alanine aminotransferase (ALT) transfers an amino group from glutamate to pyruvate, forming alanine. The glutamate largely comes from the breakdown of leucine, isoleucine and valine in muscle. Source 1, 2, 3
3. Alanine → Alanine in the blood The muscle releases alanine into the blood. By this route, carbon and nitrogen leave the muscle together without free ammonium being formed. Source 1, 2
4. Alanine in the liver → Pyruvate in the liver ALT · Vitamin B6 (PLP) In the liver the same reaction runs in reverse: ALT passes the amino group of alanine to α-ketoglutarate. Pyruvate remains. Source 1, 2
5. Pyruvate in the liver → New glucose Pyruvate carboxylase · Biotin, ATP From pyruvate, the liver rebuilds glucose via gluconeogenesis. The first step, pyruvate carboxylase, needs biotin. The glucose enters the blood — the cycle is complete. Source 4, 1
6. Alanine in the liver → Glutamate ALT · α-Ketoglutarate The amino group handed on ends up on α-ketoglutarate, which becomes glutamate. This is how nitrogen from the muscle arrives in the liver. Source 2, 6
7. Glutamate → Ammonium Glutamate dehydrog. · NAD⁺ Glutamate dehydrogenase removes the amino group as ammonium and releases α-ketoglutarate, which is then available again. Source 5, 6
8. Ammonium → Urea Urea cycle · ATP In the urea cycle, the liver cell incorporates ammonium into urea; the first step uses ATP. Urea dissolves readily in water and leaves the body via the kidney. Source 7, 6

Cofactors in this pathway

• Vitamin B6 — As pyridoxal phosphate, cofactor of alanine aminotransferase (ALT) in muscle and liver Source 8In the ORY catalogue as a laboratory value: Vitamin B6
• Glutamate — Donates the amino group to pyruvate in muscle, forming alanine Source 1, 2In the ORY catalogue as a laboratory value: Glutamat
• alpha-Ketoglutarate — Accepts the amino group of alanine in the liver, becoming glutamate Source 2, 5In the ORY catalogue as a laboratory value: Alpha-Ketoglutarat (2-Oxoglutarat)
• Leucine, isoleucine, valine — Their breakdown in muscle supplies the amino groups for glutamate and thus for alanine Source 3In the ORY catalogue as a laboratory value: Leucin
• Biotin — Cofactor of pyruvate carboxylase, the first step of gluconeogenesis from pyruvate Source 9
• Magnesium — Pyruvate carboxylase converts pyruvate with MgATP and bicarbonate into oxaloacetate Source 9In the ORY catalogue as a laboratory value: Magnesium
• NAD⁺ — Accepts hydrogen at glutamate dehydrogenase in the liver Source 5In the ORY catalogue as a laboratory value: NAD⁺ (Nicotinamidadenindinukleotid)

Sources

1. Felig P. The glucose-alanine cycle. Metabolism 1973 · PubMed 4567003
2. Palmer TN, Caldecourt MA et al. Alanine and inter-organ relationships in branched-chain amino and 2-oxo acid metabolism. Review. Biosci Rep 1985 · PubMed 3938302
3. Holeček M. Branched-chain amino acids in health and disease: metabolism, alterations in blood plasma, and as supplements. Nutr Metab (Lond) 2018 · PubMed 29755574
4. Rui L. Energy metabolism in the liver. Compr Physiol 2014 · PubMed 24692138
5. Treberg JR, Banh S et al. Intertissue differences for the role of glutamate dehydrogenase in metabolism. Neurochem Res 2014 · PubMed 23412807
6. Adeva MM, Souto G et al. Ammonium metabolism in humans. Metabolism 2012 · PubMed 22921946
7. Morris SM Jr. Regulation of enzymes of the urea cycle and arginine metabolism. Annu Rev Nutr 2002 · PubMed 12055339
8. Vanderlinde RE. Review of pyridoxal phosphate and the transaminases in liver disease. Ann Clin Lab Sci 1986 · PubMed 3008634
9. Jitrapakdee S, St Maurice M, Rayment I et al. Structure, mechanism and regulation of pyruvate carboxylase. Biochem J 2008 · PubMed 18613815

Related pathways

• GABA, glutamate and glutamine — glutamate
• Vitamin B6 — alanine
• Helicobacter pylori — urea
• Glycine and serine — Vitamin B6, Glutamat
• Branched-chain amino acids — Vitamin B6, Alpha-Ketoglutarat (2-Oxoglutarat)

As of 2026-09-16. Draft, written by Claude to schema v2; sources checked in PubMed; expert approval pending
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