Serin: the pathway in the body

Serin is part of the pathway “Glycine and serine”. This page shows the whole pathway; the station of Serin is highlighted.

Where this laboratory value sits: Serine — amino acid. 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

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

Whole pathway: Glycine and serine

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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