IUBMB Enzyme Nomenclature


Accepted name: juglone 3-hydroxylase

Reaction: 2 juglone + O2 = 2 3,5-dihydroxy-1,4-naphthoquinone (overall reaction)
(1a) 2 juglone + 2 H2O = 2 naphthalene-1,2,4,8-tetrol
(1b) 2 naphthalene-1,2,4,8-tetrol + O2 = 2 3,5-dihydroxy-1,4-naphthoquinone + 2 H2O

Glossary: juglone = 5-hydroxy-1,4-naphthoquinone

Other name(s): juglone hydroxylase; naphthoquinone hydroxylase; naphthoquinone-hydroxylase

Systematic name: 5-hydroxy-1,4-naphthoquinone,water:oxygen oxidoreductase (3-hydroxylating)

Comments: Even though oxygen is consumed, molecular oxygen is not incorporated into the product. Catalysis starts by incorporation of an oxygen atom from a water molecule into the substrate. The naphthalene-1,2,4,8-tetrol intermediate is then oxidized by molecular oxygen, which is reduced to water. Also acts on 1,4-naphthoquinone, naphthazarin and 2-chloro-1,4-naphthoquinone.

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


1. Rettenmaier, H. and Lingens, F. Purification and some properties of two isofunctional juglone hydroxylases from Pseudomonas putida J1. Biol. Chem. Hoppe-Seyler 366 (1985) 637-646. [PMID: 4041238]

[EC created 1989 as EC, transferred 2016 to EC]

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