module: dmel_sulfide_oxidation
title: Mitochondrial sulfide oxidation in Drosophila melanogaster
label: Sulfide oxidation
module_type: METABOLIC_PATHWAY
description: >-
  Hydrogen sulfide produced by cysteine catabolism and gut microbes is
  detoxified in the mitochondrial matrix. Sulfide:quinone oxidoreductase (Sqor)
  oxidises sulfide to a protein-bound persulfide, passing the electrons to
  ubiquinone in the respiratory chain. The persulfide sulfur is then oxidised to
  sulfite by the persulfide dioxygenase ETHE1 (CG30022 in flies) or transferred
  to sulfite to form thiosulfate. Sulfite oxidase (shop) oxidises sulfite to
  sulfate, and the mitochondrial dicarboxylate carrier (Dic1) can export
  thiosulfate and sulfate in exchange for other anions.
summary: >-
  Mitochondrial oxidation of hydrogen sulfide through persulfide and sulfite to
  thiosulfate and sulfate.
concepts:
  - {id: GO:0019418, label: sulfide oxidation}
cellular_components:
  - {id: GO:0005759, label: mitochondrial matrix}
parts:
  - id: sulfide_quinone_oxidation
    label: Sulfide:quinone oxidoreduction
    role: step 1, sulfide to persulfide with electron transfer to ubiquinone
    module_type: REACTION
    genes: [Sqor]
    function: {id: GO:0070224, label: sulfide:quinone oxidoreductase activity}
  - id: persulfide_dioxygenation
    label: Persulfide dioxygenation
    role: step 2, persulfide sulfur to sulfite
    module_type: REACTION
    genes: [CG30022]
    function: {id: GO:0050313, label: sulfur dioxygenase activity}
  - id: sulfite_oxidation
    label: Sulfite oxidation
    role: step 3, sulfite to sulfate
    module_type: REACTION
    genes: [shop]
    function: {id: GO:0008482, label: sulfite oxidase activity}
  - id: anion_export
    label: Thiosulfate and sulfate export
    role: export of oxidised sulfur anions from the matrix
    module_type: TRANSPORT_STEP
    genes: [Dic1]
    function: {id: GO:0015117, label: thiosulfate transmembrane transporter activity}
connections:
  - source: sulfide_quinone_oxidation
    target: persulfide_dioxygenation
    connection_type: PRECEDES
    description: The persulfide made by Sqor is oxidised by ETHE1.
  - source: persulfide_dioxygenation
    target: sulfite_oxidation
    connection_type: PRECEDES
    description: Sulfite is oxidised to sulfate by sulfite oxidase.
  - source: sulfite_oxidation
    target: anion_export
    connection_type: PROVIDES_INPUT_FOR
    description: Sulfate and thiosulfate leave the matrix through the dicarboxylate carrier.
notes: >-
  Boundary. The sulfurtransferase (rhodanese) step that makes thiosulfate is
  not in the FlyBase group and is not modelled. CG30022 is the fly ortholog of
  ETHE1 (UniProt names it persulfide dioxygenase ETHE1); its activity and those
  of Sqor follow orthology and have not been assayed in flies. Dic1 transport of thiosulfate, sulfate and dicarboxylates
  has been shown in reconstituted proteoliposomes; Dic1 also transports malate,
  succinate and phosphate, so its role here is one of several. Sulfite oxidase
  also handles sulfite from cysteine catabolism.