IUBMB Enzyme Nomenclature


Accepted name: carotenoid φ-ring synthase

Reaction: carotenoid β-end group + 2 acceptor = carotenoid φ-end group + 2 reduced acceptor

For diagram of reaction click here.

Glossary: chlorobactene = φ,ψ-carotene
β-isorenieratene = φ,β-carotene
isorenieratene = φ,φ-carotene

Other name(s): crtU (gene name) (ambiguous)

Systematic name: carotenoid β-ring:acceptor oxidoreductase/methyltranferase (φ-ring forming)

Comments: The enzyme, found in green sulfur bacteria, some cyanobacteria and some actinobacteria, introduces additional double bonds to the carotenoid β-end group, leading to aromatization of the ionone ring. As a result, one of the methyl groups at C-1 is transferred to position C-2. It is involved in the biosynthesis of carotenoids with φ-type aromatic end groups such as chlorobactene, β-isorenieratene, and isorenieratene.

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


1. Moshier, S.E. and Chapman, D.J. Biosynthetic studies on aromatic carotenoids. Biosynthesis of chlorobactene. Biochem. J. 136 (1973) 395-404. [PMID: 4774401]

2. Krugel, H., Krubasik, P., Weber, K., Saluz, H.P. and Sandmann, G. Functional analysis of genes from Streptomyces griseus involved in the synthesis of isorenieratene, a carotenoid with aromatic end groups, revealed a novel type of carotenoid desaturase. Biochim. Biophys. Acta 1439 (1999) 57-64. [PMID: 10395965]

3. Frigaard, N.U., Maresca, J.A., Yunker, C.E., Jones, A.D. and Bryant, D.A. Genetic manipulation of carotenoid biosynthesis in the green sulfur bacterium Chlorobium tepidum. J. Bacteriol. 186 (2004) 5210-5220. [PMID: 15292122]

[EC created 2018]

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