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. Author manuscript; available in PMC: 2019 Aug 15.
Published in final edited form as: Nat Prod Rep. 2018 Aug 15;35(8):792–837. doi: 10.1039/c7np00067g

Fig. 21.

Fig. 21

Multiple oxidative modifications in the astaxanthin 189 biosynthetic pathway involving two αKG-dependent NHFe enzymes: CtrZ and CrtW. CrtZ hydroxylates either the 3 or 3′ position of the β-ionone ring, while CrtW oxidizes methylene to keto groups at the 4 or 4′ position of the β-ionone ring.263