Component

SEPSECS / SepSecS

Enzyme that converts the phosphorylated serine-tRNA precursor into Sec-tRNA.

4 recorded relationships. Experimental role, claim status and evidence remain attached to each record.

Read recorded mechanisms Open recursive mind map

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.

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

What it acts on

  1. Human SepSecS structural and functional analysis supported correct positioning of tRNA-bound phosphoserine, but not free phosphoserine, for PLP-dependent selenocysteine formation.

    SEPSECS / SepSecS → O-phosphoseryl-tRNA Sec source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human SepSecS–tRNA complex structure with enzyme assays.
    limitations
    Free phosphoserine and a phosphoserine residue on this specialized tRNA are not interchangeable substrates.
    nutrient_topic
    L-Serine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Serine
    plain_language
    The carrier and the cofactor are part of the reaction, not optional packaging.
    primary_references
    The human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19608919/ · DOI 10.1126/science.1173755

    L-Serine: synthesis, one-carbon metabolism, lipids and cross-nutrient mechanisms (2026-09-19) · lines 390–396

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human SepSecS–tRNA complex structure with enzyme assays. · source_derived_draft · unverified_draft

    ## l-serine-sepsecs-substrate The carrier and the cofactor are part of the reaction, not optional packaging. Human SepSecS structural and functional analysis supported correct positioning of tRNA-bound phosphoserine, but not free phosphoserine, for PLP-dependent selenocysteine formation. Model: Human SepSecS–tRNA complex structure with enzyme assays. Limitations: Free phosphoserine and a phosphoserine residue on this specialized tRNA are not interchangeable substrates. Evidence access: Primary abstract The human SepSecS-tRNASec complex reveals the mechanism of selenocysteine formation. · 2009 · https://pubmed.ncbi.nlm.nih.gov/19608919/ · DOI 10.1126/science.1173755
    Complete structured claim and evidence

  2. Pathogenic SEPSECS impairment can disrupt Sec-tRNA synthesis.

    SEPSECS / SepSecS → Sec-tRNA[Ser]Sec source_derived_draftsource_reported: Human genetic and biochemical evidence as summarized in the supplied source; unverified synthesis.
    Experimental context and source evidence
    availability_state
    Pathogenic SEPSECS impairment affecting Sec-tRNA synthesis.
    experimental_scope
    Rare human genetic disorders and the defined Sec-tRNA biosynthetic pathway.
    limitations
    This is not ordinary selenium dietary deficiency. SEPSECS being the SLA/LP autoantigen does not make autoimmune hepatitis a selenium-deficiency disease.
    trigger_kind
    machinery_impairment

    Selenium deficiency: a mechanism-first reference · lines 23–43

    Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft

    Selenocysteine (Sec) is unusual because it is synthesized on its own tRNA rather than existing as a large free amino-acid pool. There is no dedicated Sec-tRNA synthetase. Instead, two biosynthetic branches converge: Serine + tRNA^[Ser]Sec ↓ SerRS Ser-tRNA^[Ser]Sec ↓ PSTK PSer-tRNA^[Ser]Sec ────────────────────────┐ │ Selenide + ATP │ ↓ SEPHS2 │ selenophosphate ───────────────────────────┤ ↓ SEPSECS Sec-tRNA^[Ser]Sec ↓ eEFSec ribosome reaches UGA ↓ SECIS + SECISBP2/SBP2 machinery ↓ SELENOCYSTEINE INSERTED SerRS charging tRNA^[Ser]Sec with serine is an obligatory biosynthetic step, not a mistake. SEPHS2 supplies selenophosphate, while PSTK and SEPSECS convert the serine-charged tRNA into Sec-tRNA^[Ser]Sec.

    Selenium deficiency: a mechanism-first reference · lines 541–545

    Supplied selenium deficiency reference · supports · Supplied reference; verify the primary study and experimental context. · source_derived_draft · unverified_draft

    SEPSECS Sec-tRNA synthesis defect Pontocerebellar hypoplasia spectrum
    Complete structured claim and evidence

  3. PLP-dependent SEPSECS converts phosphoseryl-tRNA Sec to Sec-tRNA through phosphate elimination and selenium donation from selenophosphate, not incorporation of intact selenophosphate.

    SEPSECS / SepSecS → Sec-tRNA[Ser]Sec source_derived_draftliterature_reviewed:direct_experimental
    Experimental context and source evidence
    cell_type
    Purified enzyme/tRNA
    experimental_model
    Human enzyme/tRNA crystallography and biochemical assays
    limitations
    Not a measurement of dietary intake effects.
    organism
    Homo sapiens

    Selenium: literature corrections and mechanism additions · lines 1154–1164

    Metabolic Ledger literature curation, 17 September 2026; primary papers linked individually · supports · Human enzyme/tRNA crystallography and biochemical assays · secondary_verified · secondary_verified

    ## sepsecs-chemistry SEPSECS uses selenium from the donor to finish the tRNA-bound amino acid. PLP-dependent SEPSECS converts phosphoseryl-tRNA Sec to Sec-tRNA through phosphate elimination and selenium donation from selenophosphate, not incorporation of intact selenophosphate. Organism: Homo sapiens Cell type: Purified enzyme/tRNA Experimental model: Human enzyme/tRNA crystallography and biochemical assays Limitations: Not a measurement of dietary intake effects. Primary reference: [The human SepSecS–tRNASec complex reveals mechanism of selenocysteine formation](https://pubmed.ncbi.nlm.nih.gov/19608919/)
    Complete structured claim and evidence

Where it participates (unsigned role)

  1. Human SerRS also attached L-serine to tRNA Sec, initiating the specialized pathway that later converts its attached amino acid into selenocysteine.

    Human cytosolic seryl-tRNA synthetase / SARS1 → Seryl-tRNA Sec source_derived_draftungraded
    Experimental context and source evidence
    evidence_access
    Primary abstract
    experimental_model
    Human cytosolic SerRS substrate-recognition and aminoacylation experiments.
    limitations
    Serylation does not itself add selenium; PSTK and SEPSECS act in later steps.
    nutrient_topic
    L-Serine collection; species, compartment, exposure, co-substrates and manipulation remain explicit. · L-Serine
    plain_language
    The same loading enzyme feeds both ordinary protein synthesis and selenium-dependent decoding.
    primary_references
    Insights into substrate promiscuity of human seryl-tRNA synthetase. · 2017 · https://pubmed.ncbi.nlm.nih.gov/28808125/ · DOI 10.1261/rna.061069.117

    L-Serine: synthesis, one-carbon metabolism, lipids and cross-nutrient mechanisms (2026-09-19) · lines 454–460

    AI-assisted research curation; primary references, access levels and experimental limitations individually identified. Not publisher full text. · supports · Human cytosolic SerRS substrate-recognition and aminoacylation experiments. · source_derived_draft · unverified_draft

    ## l-serine-serrs-selenium-route The same loading enzyme feeds both ordinary protein synthesis and selenium-dependent decoding. Human SerRS also attached L-serine to tRNA Sec, initiating the specialized pathway that later converts its attached amino acid into selenocysteine. Model: Human cytosolic SerRS substrate-recognition and aminoacylation experiments. Limitations: Serylation does not itself add selenium; PSTK and SEPSECS act in later steps. Evidence access: Primary abstract Insights into substrate promiscuity of human seryl-tRNA synthetase. · 2017 · https://pubmed.ncbi.nlm.nih.gov/28808125/ · DOI 10.1261/rna.061069.117
    Complete structured claim and evidence

In the sources

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

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

    Evidence, AI assistance and curation standards