Nature Communications 2015-01-01

A highly selective biosynthetic pathway to non-natural C50 carotenoids assembled from moderately selective enzymes.

Maiko Furubayashi, Mayu Ikezumi, Shinichi Takaichi, Takashi Maoka, Hisashi Hemmi, Takuya Ogawa, Kyoichi Saito, Alexander V Tobias, Daisuke Umeno

Index: Nat. Commun. 6 , 7534, (2015)

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Abstract

Synthetic biology aspires to construct natural and non-natural pathways to useful compounds. However, pathways that rely on multiple promiscuous enzymes may branch, which might preclude selective production of the target compound. Here, we describe the assembly of a six-enzyme pathway in Escherichia coli for the synthesis of C50-astaxanthin, a non-natural purple carotenoid. We show that by judicious matching of engineered size-selectivity variants of the first two enzymes in the pathway, farnesyl diphosphate synthase (FDS) and carotenoid synthase (CrtM), branching and the production of non-target compounds can be suppressed, enriching the proportion of C50 backbones produced. We then further extend the C50 pathway using evolved or wild-type downstream enzymes. Despite not containing any substrate- or product-specific enzymes, the resulting pathway detectably produces only C50 carotenoids, including ∼ 90% C50-astaxanthin. Using this approach, highly selective pathways can be engineered without developing absolutely specific enzymes.