Prostaglandin H synthase compound I: molecular mechanisms & dependencies

How nutrients influence it

Every nutrient with a recorded effect on this component, credited to the nutrient that acted rather than the chapter that recorded it. Open a nutrient to see the findings and the conditions they were measured under.

Human evidence only

How nutrients reach it in more than one step

Chains of two or more recorded steps that end here, grouped by the nutrient they start from. Each step is a separate finding, so a chain is a route a mechanism could take, not proof that it does.

Tracing routes…

What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

Where it participates (unsigned role)

Reduction of prostaglandin H synthase compound II to native enzyme by phenol proceeded with a second-order rate constant of 5.3 x 10(5) per molar per second and by hydroquinone at 2.1 x 10(6), rapid scan spectra also showed reduction of compound I to compound II by both so that reduction of both compounds is a one-electron process, and the results suggest the tyrosyl radical detected in the presence of oxidizing agents is formed by intramolecular electron transfer from the tyrosyl residue to the porphyrin pi-cation radical and tends to disappear in the presence of sufficient reducing substrate.
A reducing cosubstrate of the peroxidase → Prostaglandin H synthase compound II source_derived_draftungraded
Experimental context and source evidence
evidence_span
{"source_cache": "artifacts/paracetamol-research/1727638.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "028284c7b657c213a3052d362a0a5d050b1678d9ab3c5403b8e68d3631494c0c", "start_char": 0, "end_char": 1789, "text_sha256": "028284c7b657c213a3052d362a0a5d050b1678d9ab3c5403b8e68d3631494c0c"}
experimental_model
Rapid scan spectrometry and transient state kinetics of prostaglandin H synthase compound II reduction
exposure
Phenol and hydroquinone as reducing cosubstrates, with indomethacin
limitations
Measures the reduction step directly with rate constants rather than inferring it from inhibition. It uses phenol and hydroquinone rather than paracetamol, which is recorded on the claim.
nutrient_topic
Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. · Paracetamol
organism
Enzyme
plain_language
A phenol hands the enzyme one electron at a time, and enough of it makes the radical the enzyme needs disappear.
primary_references
[apap-p1727638] Reduction of prostaglandin H synthase compound II by phenol and hydroquinone, and the effect of indomethacin. (1992). https://pubmed.ncbi.nlm.nih.gov/1727638/ DOI: 10.1016/0003-9861(92)90070-d
tissue_or_cell_type
Purified prostaglandin H synthase
Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22) · lines 142–153
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Rapid scan spectrometry and transient state kinetics of prostaglandin H synthase compound II reduction · source_derived_draft · unverified_draft
### apap-one-electron-reduction Reduction of prostaglandin H synthase compound II to native enzyme by phenol proceeded with a second-order rate constant of 5.3 x 10(5) per molar per second and by hydroquinone at 2.1 x 10(6), rapid scan spectra also showed reduction of compound I to compound II by both so that reduction of both compounds is a one-electron process, and the results suggest the tyrosyl radical detected in the presence of oxidizing agents is formed by intramolecular electron transfer from the tyrosyl residue to the porphyrin pi-cation radical and tends to disappear in the presence of sufficient reducing substrate. Condition category: normal nutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. plain_language: A phenol hands the enzyme one electron at a time, and enough of it makes the radical the enzyme needs disappear. organism: Enzyme tissue_or_cell_type: Purified prostaglandin H synthase experimental_model: Rapid scan spectrometry and transient state kinetics of prostaglandin H synthase compound II reduction limitations: Measures the reduction step directly with rate constants rather than inferring it from inhibition. It uses phenol and hydroquinone rather than paracetamol, which is recorded on the claim. exposure: Phenol and hydroquinone as reducing cosubstrates, with indomethacin evidence_span: {"source_cache": "artifacts/paracetamol-research/1727638.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "028284c7b657c213a3052d362a0a5d050b1678d9ab3c5403b8e68d3631494c0c", "start_char": 0, "end_char": 1789, "text_sha256": "028284c7b657c213a3052d362a0a5d050b1678d9ab3c5403b8e68d3631494c0c"} [apap-p1727638] Reduction of prostaglandin H synthase compound II by phenol and hydroquinone, and the effect of indomethacin. (1992). https://pubmed.ncbi.nlm.nih.gov/1727638/ DOI: 10.1016/0003-9861(92)90070-d
Complete structured claim and evidence
Relatively low concentrations of acetaminophen from 20 to 200 micromolar stimulate prostaglandin H synthase activity in ram seminal vesicle microsomes whereas concentrations above 10 millimolar inhibit the conversion of arachidonic acid to prostaglandin G2, both activities apparently involving reduction of oxidized complexes of the enzyme and roughly correlating with the electrochemical half-wave oxidation potentials of a series of hydroxyacetanilides, consistent with common intermediate enzyme forms for both cyclooxygenase and hydroperoxidase catalysed reactions of which one is reduced at low drug concentrations to stimulate and another at higher concentrations to inhibit.
Paracetamol → Cyclooxygenase-1 (PTGS1) source_derived_draftungraded
Experimental context and source evidence
evidence_span
{"source_cache": "artifacts/paracetamol-research/3124965.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "dcc85a1ab66984973092042b5553f43fbbe5eb10b674614c9b1fa991b3969502", "start_char": 0, "end_char": 2236, "text_sha256": "dcc85a1ab66984973092042b5553f43fbbe5eb10b674614c9b1fa991b3969502"}
experimental_model
Ram seminal vesicle microsomal prostaglandin H synthase with product identification by cooxidation
exposure
Acetaminophen from 20 micromolar to above 10 millimolar, with glutathione, ascorbate and indomethacin
limitations
Shows that the drug both stimulates and inhibits the same enzyme depending on concentration, and that the enzyme makes NAPQI from it. A microsomal preparation at concentrations far above therapeutic.
nutrient_topic
Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. · Paracetamol
organism
Sheep
plain_language
At low concentrations the drug feeds the enzyme and at high concentrations it stalls it, both by handing over electrons.
primary_references
[apap-p3124965] Acetaminophen and analogs as cosubstrates and inhibitors of prostaglandin H synthase. (1988). https://pubmed.ncbi.nlm.nih.gov/3124965/ DOI: 10.1016/0009-2797(88)90101-9
tissue_or_cell_type
Seminal vesicle microsomes
Paracetamol: the enzyme it reduces rather than blocks, the isoform that turned out not to exist, the metabolite that carries the analgesia, and the metabolite that destroys the liver (2026-09-22) · lines 116–127
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Ram seminal vesicle microsomal prostaglandin H synthase with product identification by cooxidation · source_derived_draft · unverified_draft
### apap-stimulates-then-inhibits Relatively low concentrations of acetaminophen from 20 to 200 micromolar stimulate prostaglandin H synthase activity in ram seminal vesicle microsomes whereas concentrations above 10 millimolar inhibit the conversion of arachidonic acid to prostaglandin G2, both activities apparently involving reduction of oxidized complexes of the enzyme and roughly correlating with the electrochemical half-wave oxidation potentials of a series of hydroxyacetanilides, consistent with common intermediate enzyme forms for both cyclooxygenase and hydroperoxidase catalysed reactions of which one is reduced at low drug concentrations to stimulate and another at higher concentrations to inhibit. Condition category: normal nutrient_topic: Paracetamol research collection; topical membership is not evidence of a direct clinical effect, and the drug is recorded separately from the metabolites NAPQI and AM404. plain_language: At low concentrations the drug feeds the enzyme and at high concentrations it stalls it, both by handing over electrons. organism: Sheep tissue_or_cell_type: Seminal vesicle microsomes experimental_model: Ram seminal vesicle microsomal prostaglandin H synthase with product identification by cooxidation limitations: Shows that the drug both stimulates and inhibits the same enzyme depending on concentration, and that the enzyme makes NAPQI from it. A microsomal preparation at concentrations far above therapeutic. exposure: Acetaminophen from 20 micromolar to above 10 millimolar, with glutathione, ascorbate and indomethacin evidence_span: {"source_cache": "artifacts/paracetamol-research/3124965.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "dcc85a1ab66984973092042b5553f43fbbe5eb10b674614c9b1fa991b3969502", "start_char": 0, "end_char": 2236, "text_sha256": "dcc85a1ab66984973092042b5553f43fbbe5eb10b674614c9b1fa991b3969502"} [apap-p3124965] Acetaminophen and analogs as cosubstrates and inhibitors of prostaglandin H synthase. (1988). https://pubmed.ncbi.nlm.nih.gov/3124965/ DOI: 10.1016/0009-2797(88)90101-9
Complete structured claim and evidence

The events it takes part in

A mechanism often involves more than two components. These are the full events, with every participant and its role.

Situations it appears in

Low-supply and faulty-machinery situations recorded in the chapters where this component plays a part.

In the sources

Preserved passages that mention this component, quoted exactly. Open one to read it in context.

Open hypotheses

Proposed ideas that involve this component. They are labeled as hypotheses and do not change any recorded statement.

This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.

Prostaglandin H synthase compound I