EC - Plastoquinol—plastocyanin reductase

  IntEnz view ENZYME view

IntEnz Enzyme Nomenclature


Accepted name:
plastoquinol—plastocyanin reductase
Other names:
cytochrome b6-f complex
cytochrome b6/f complex
plastoquinol/plastocyanin oxidoreductase
cytochrome b6f complex
Systematic name:
plastoquinol:oxidized-plastocyanin oxidoreductase



Contains two b-type cytochromes, two c-type cytochromes (cn and f), and a [2Fe-2S] Rieske cluster. The enzyme plays a key role in photosynthesis, transferring electrons from photosystem II (EC to photosystem I (EC Cytochrome c-552 can act as acceptor instead of plastocyanin, but more slowly. In chloroplasts, protons are translocated through the thylakoid membrane from the lumen to the stroma. The mechanism occurs through the Q cycle as in EC, quinol—cytochrome-c reductase (complex III) and involves electron bifurcation. Formerly EC

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0009496
CAS Registry Number: 79079-13-3
UniProtKB/Swiss-Prot: (55) [show] [UniProt]


  1. Hurt, E. and Hauska, G.
    A cytochrome f/b6 complex of five polypeptides with plastoquinol-plastocyanin-oxidoreductase activity from spinach chloroplasts.
    Biochem. J. 117: 591-595 (1981). [PMID: 6269845]
  2. Cramer, W. A., Zhang, H.
    Consequences of the structure of the cytochrome b6f complex for its charge transfer pathways.
    Biochim. Biophys. Acta 1757: 339-345 (2006). [PMID: 16787635]

[EC created 1984 as EC, transferred 2011 to EC]