Glycine and serine: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Glycine, serine: 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

Glycine and serine are amino acids that the body can also make itself. They supply one-carbon units and are building blocks of proteins, membranes and glutathione.

The pathway step by step

1. 3-Phosphoglycerate → 3-Phosphohydroxypyruvate PHGDH · NAD⁺ Phosphoglycerate dehydrogenase (PHGDH) turns the OH group into a keto group and transfers the hydrogen to NAD⁺. Source 1
2. 3-Phosphohydroxypyruvate → 3-Phosphoserine PSAT1 · Vitamin B6 (PLP), Glutamate The aminotransferase PSAT1 transfers an amino group from glutamate to the molecule. It works with pyridoxal phosphate, the active form of vitamin B6. Source 1
3. 3-Phosphoserine → Serine PSPH · Magnesium The phosphatase PSPH removes the phosphate group, forming serine. Serine also comes from food and from the breakdown of the body’s own proteins. Source 1
4. Serine → Glycine SHMT · Vitamin B6 (PLP), THF (folate) Serine hydroxymethyltransferase (SHMT) removes a one-carbon unit from serine and transfers it to tetrahydrofolate. Glycine remains. Source 2, 3
5. Glycine → Glycine as a component Glycine is a building block of glutathione, haem and creatine and is also attached to bile acids. In the collagen of connective tissue, every third position in the chain is a glycine. Source 4, 3
6. Glycine cleavage system → 5,10-Methylene-THF Glycine cleavage · THF (folate), NAD⁺ The one-carbon unit is now attached to tetrahydrofolate. From there it is used to build DNA components and to form methyl groups. Source 2

Cofactors in this pathway

• Vitamin B6 (PLP) — Cofactor of PSAT1, serine hydroxymethyltransferase and the glycine cleavage system Source 1, 2In the ORY catalogue as a laboratory value: Vitamin B6
• Folate (THF) — As tetrahydrofolate, accepts the one-carbon unit from serine and glycine Source 2In the ORY catalogue as a laboratory value: Folsäure
• NAD⁺ — Accepts hydrogen at PHGDH and in the glycine cleavage system Source 1, 2In the ORY catalogue as a laboratory value: NAD⁺ (Nicotinamidadenindinukleotid)
• Glutamate — Donates the amino group for 3-phosphoserine at PSAT1 Source 1In the ORY catalogue as a laboratory value: Glutamat
• Magnesium — Metal ion of the phosphatase PSPH, which turns 3-phosphoserine into serine Source 1In the ORY catalogue as a laboratory value: Magnesium
• Lipoic acid — Bound to a protein of the glycine cleavage system, where it passes on intermediates Source 3

Sources

1. Murtas G, Marcone GL, Sacchi S et al. L-serine synthesis via the phosphorylated pathway in humans. Cell Mol Life Sci 2020 · PubMed 32594192
2. Ducker GS, Rabinowitz JD. One-Carbon Metabolism in Health and Disease. Cell Metab 2017 · PubMed 27641100
3. Holeček M. Glycine as a conditionally essential amino acid and its relationship to l-serine. Metabolism 2025 · PubMed 40527450
4. Wang W, Wu Z, Dai Z et al. Glycine metabolism in animals and humans: implications for nutrition and health. Amino Acids 2013 · PubMed 23615880

Related pathways

• Folic acid — 5,10-methylene-thf
• Methylation: methionine and homocysteine — 5,10-methylene-thf
• Alanine — Vitamin B6, NAD⁺ (Nicotinamidadenindinukleotid)
• GABA, glutamate and glutamine — Vitamin B6, NAD⁺ (Nicotinamidadenindinukleotid)
• Dopamine, noradrenaline, adrenaline — Vitamin B6, NAD⁺ (Nicotinamidadenindinukleotid)

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