Functional characterization of fatty acid synthase inHermetia illucens

Abstract

AbstractFatty acid synthase (FAS) is a key role inde novolipogenesis (DNL) in most lives. In insects, type I FAS functions in homodimer, activated by a phosphopantetheine transferase (PPT), tode novoproduce essential saturated fatty acid for cellular processes. In a nova insect speciesHermetia illucens(Diptera: Stratiomyidae), different from most animals and insects, lauric acid (LA) accumulates to a noticeable level, near content of that in coconut oil or palm kernel oil. However, the origin of LA, fromde novobiosynthesis or as degraded products from long chain fatty acid, was still ambiguous. Here, in this study, we mined aFASgenes (HiOGS16234) fromH. illucensgenome and initially characterized its abilities of LA production in a free-fatty-acid producible yeast. After clear the yeast metabolites background of fatty acid by deletion ofScFAS1andScELO1sequentially, which responsible for fatty acid genesis and elongation respectively, functions of HiOGS16234 fromH. illucenswasin vitroelucidated by analyzing its product portfolio. Through protein domain swap in HiOGS16234, we found the ketoacyl synthase domain and thioesterases domain were responsible for the different product portfolio of HiOGS16234, compared with DmFASN1. Throughin vitroassay in yeast, the origin of LA in BSF was firstly elucidated at molecular level, which support DNL origin hypothesis in BSF.