Coenzyme Q10: the pathway in the body

This page shows the biochemical pathway behind the laboratory value Coenzyme Q10 (ubiquinol): 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

Coenzyme Q10 is a fat-soluble molecule with a ring and a chain of ten isoprene units. In the inner mitochondrial membrane it carries electrons from one respiratory chain complex to the next.

The pathway step by step

1. Acetyl-CoA → Mevalonate HMG-CoA reductase · NADPH Mevalonate is formed via HMG-CoA. This stretch supplies not only cholesterol but also the building blocks for the tail of Q10. Source 4, 1
2. Mevalonate → Farnesyl-PP FPP synthase Mevalonate gives rise to activated isoprene units, which are linked to form farnesyl pyrophosphate. Several pathways branch off here. Source 1
3. Farnesyl-PP → Decaprenyl-PP PDSS1, PDSS2 Two enzymes extend the chain to ten isoprene units. Hence the name Q10: in humans the molecule carries ten of these building blocks. Source 1
4. Decaprenyl-PP → Ubiquinone (Q10) COQ2 and COQ enzymes The enzyme COQ2 attaches the chain to a ring of 4-hydroxybenzoate. Further COQ enzymes modify the ring in the mitochondrion; ubiquinone is then complete. Source 1
5. Ubiquinone (Q10) → Q10 in the blood · Lipoproteins In the blood, Q10 travels in lipoproteins, mostly in its reduced form, ubiquinol. The body makes most of it itself; a smaller part comes from food. Source 2
6. Ubiquinone → Ubiquinol Complexes I and II · NADH, FADH2 Complex I and complex II pass electrons from NADH and FADH2 to Q10. With two electrons and two protons, ubiquinol is formed. Source 2
7. Ubiquinol → Complex III · Cytochrome c Complex III takes over the electrons and hands them on via cytochrome c. Q10 is then oxidised again and starts over. Source 2
8. Complex III → Proton gradient With each round, protons are pumped out of the matrix. This builds up a gradient across the inner mitochondrial membrane. Source 2
9. Proton gradient → ATP ATP synthase · ADP The protons flow back through ATP synthase. Its rotation joins ADP and phosphate to form ATP. Source 2
10. Ubiquinol → Membrane lipids Ubiquinol also donates electrons outside the respiratory chain. It traps radicals in membranes and so interrupts the chain reaction of lipid oxidation. Source 2

Cofactors in this pathway

• Tyrosine — Supplies the 4-hydroxybenzoate ring, the part of the molecule that accepts electrons Source 1In the ORY catalogue as a laboratory value: Tyrosin
• NADPH — Electron donor of HMG-CoA reductase on the way to the isoprene tail Source 4
• SAM (from methionine) — Methyl group donor of the COQ enzymes that modify the ring of the molecule Source 1In the ORY catalogue as a laboratory value: Methionin
• NAD⁺ — As NADH, the electron source for complex I, which passes them to Q10 Source 2In the ORY catalogue as a laboratory value: NAD⁺ (Nicotinamidadenindinukleotid)
• FAD (vitamin B2) — As FADH₂, the electron source for complex II, which passes them to Q10 Source 2
• Vitamin E — Ubiquinol passes electrons to oxidised tocopherol; both sit in the same membrane Source 2In the ORY catalogue as a laboratory value: Vitamin E (Tocopherol)

What acts on this pathway

• Statins — Statins inhibit HMG-CoA reductase, which also stands at the start of the Q10 pathway. Lower Q10 levels in the blood have been described with statins; part of this follows the lipoproteins in which Q10 travels. Source 3

Sources

1. Guerra RM, Pagliarini DJ. Coenzyme Q biochemistry and biosynthesis. Trends Biochem Sci 2023 · PubMed 36702698
2. Wang Y, Lilienfeldt N, Hekimi S. Understanding coenzyme Q. Physiol Rev 2024 · PubMed 38722242
3. Nawarskas JJ. HMG-CoA reductase inhibitors and coenzyme Q10. Cardiol Rev 2005 · PubMed 15705257
4. Sharpe LJ, Brown AJ. Controlling cholesterol synthesis beyond 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). J Biol Chem 2013 · PubMed 23696639

Related pathways

• Cholesterol and lipoproteins — mevalonate
• Carnitine — Methionin, NAD⁺ (Nicotinamidadenindinukleotid)
• Estradiol — Methionin, NAD⁺ (Nicotinamidadenindinukleotid)
• Dopamine, noradrenaline, adrenaline — Methionin, NAD⁺ (Nicotinamidadenindinukleotid)
• Estrogen breakdown — Methionin, NAD⁺ (Nicotinamidadenindinukleotid)

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