Xi Xie
University of Saskatchewan, Canada
Title: Ketoacylsynthase domains of a PUFA synthase in Thraustochytrium can function as standalone enzymes in Escherichia coli
Biography
Biography: Xi Xie
Abstract
Thraustochytrium sp. 26185 accumulates a high level of docosahexaenoic acid (DHA), a nutritionally important w-3 very long chain unsaturated fatty acid (VLCPUFAs) synthesized primarily by a polyunsaturated fatty acid (PUFA) synthase. However, the molecular mechanism of the PUFA synthase for positioning multiple cis-double bonds in the acyl chain remains elusive. 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 retaining double bonds in the extended acyl chain. To investigate the function of these putative KS domains, two KS domains from Subunit A (KS-A) and from Subunit B (KS-B) of the PUFA synthase were dissected and then expressed as standalone enzymes in Escherichia coli. The results showed that both KS-A and KS-B domains, but not the mutagenized ones could complement defective phenotypes of both E. coli FabB and FabF mutants.Overexpression of these domains in a wild type E. coli showed increases in the total fatty acid production. Successful complementation and functional expression of the embedded KS domains from the PUHA synthase in E. coli is the first step forward to study the molecular mechanism of the PUFA synthase for the biosynthesis of VLCPUFAs.