IUBMB Enzyme Nomenclature


Accepted name: photosystem II

Reaction: 2 H2O + 2 plastoquinone + 4 = O2 + 2 plastoquinol

Systematic name: H2O:plastoquinone reductase (light-dependent)

Comments: Contains chlorophyll a, β-carotene, pheophytin, plastoquinone, a Mn4Ca cluster, heme and non-heme iron. Four successive photoreactions, resulting in a storage of four positive charges, are required to oxidize two water molecules to one oxygen molecule.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Knaff, D.B., Malkin, R., Myron, J.C. and Stoller, M. The role of plastoquinone and β-carotene in the primary reaction of plant photosystem II. Biochim. Biophys. Acta 459 (1977) 402-411. [PMID: 849432]

2. Guskov, A., Kern, J., Gabdulkhakov, A., Broser, M., Zouni, A. and Saenger, W. Cyanobacterial photosystem II at 2.9-Å resolution and the role of quinones, lipids, channels and chloride. Nat. Struct. Mol. Biol. 16 (2009) 334-342. [PMID: 19219048]

[EC created 2011]

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