Ketoacylsynthase Domains of a Polyunsaturated Fatty Acid Synthase in Thraustochytrium sp. Strain ATCC 26185 Can Effectively Function as Stand-Alone Enzymes in Escherichia coli

• DOI: 10.1128/aem.03133-16
• Publication Date: 2017-02-18T01:55:19Z
• Authors: Xi Xie; Dauenpen Meesapyo...; Xiao Qiu
• Keywords: Polyketide synthase; Acyl carrier protein

Thraustochytrium sp. strain ATCC 26185 accumulates a high level of docosahexaenoic acid (DHA), nutritionally important ω-3 very-long-chain polyunsaturated fatty (VLCPUFA) synthesized primarily by (PUFA) synthase, type I polyketide synthase-like megaenzyme. The PUFA synthase in this species comprises three large subunits, each with multiple catalytic domains. It was hypothesized that among these domains, ketoacylsynthase (KS) domains might be critical for catalyzing the condensation specific unsaturated acyl-acyl carrier proteins (ACPs) malonyl-ACP, thereby retaining double bonds an extended acyl chain. To investigate functions putative KS two segment sequences from subunit A (KS-A) and B (KS-B) were dissected then expressed as stand-alone enzymes Escherichia coli results showed both KS-A KS-B could complement defective phenotypes E. colifabB fabF mutants. Overexpression wild-type led to increases total production. produced higher ratio acids (UFAs) saturated (SFAs), while improve overall production more effectively, particularly SFAs, implying is comparable FabF, similar FabB functions. Successful complementation functional expression embedded are first step forward studying molecular mechanism biosynthesis VLCPUFAs ThraustochytriumIMPORTANCE Very-long-chain (VLCPUFAs) human health. They can biosynthesized either aerobic pathway or anaerobic nature. However, abundant marine microorganisms megaenzyme Furthermore, fundamental enzyme synthesize still remains unknown. This report started dissecting protist expressing them mutants acyl-ACP malonyl-ACP. improved overexpression experiments indicate effectively function result has paved way further mechanisms VLCPUFAs.