Reconstitution of a Type II Polyketide Synthase that Catalyzes Polyene Formation |
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| Authors: | Danyao Du Dr. Yohei Katsuyama Dr. Kazuo Shin‐ya Dr. Yasuo Ohnishi |
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| Affiliation: | 1. Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan;2. National Institute of Advanced Industrial Science and Technology (AIST), Koto-ku, Tokyo, Japan |
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| Abstract: | While type II polyketide synthases (PKSs) are known for producing aromatic compounds, a phylogenetically new subfamily of type II PKSs have been recently proposed to synthesize polyene structures. Here we report in vitro analysis of such a type II PKS, IgaPKS for ishigamide biosynthesis. The ketoreductase (Iga13) and dehydratase (Iga16) were shown to catalyze the reduction of a β‐keto group and dehydration of a β‐hydroxy group, respectively, to form a trans double bond. Incubation of the acyl carrier protein (Iga10), the ketosynthase/chain length factor complex (Iga11–Iga12), Iga13 and Iga16 with malonyl and hexanoyl‐CoAs and NADPH followed by KOH hydrolysis resulted in the formation of four unsaturated carboxylic acids (C8, C10, C12, and C14), indicating that IgaPKS catalyzes tetraene formation by repeating the cycle of condensation, keto‐reduction and dehydration with strict stereo‐specificity. We propose “highly reducing type II PKS subfamily” for the polyene‐producing type II PKSs. |
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| Keywords: | biosynthesis polyenes polyketides Streptomyces polyketide synthases |
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