PUFA-synthase-specific PPTase enhanced the polyunsaturated fatty acid biosynthesis via the polyketide synthase pathway in Aurantiochytrium

Sen Wang,Xiaojin Song,Zhuojun Wang,Qiu Cui,Weijian Wan,Chuanzeng Lan

doi:10.1186/s13068-020-01793-x

Abstract

BackgroundPhosphopantetheinyl transferase (PPTase) can change the acyl-carrier protein (ACP) from an inactive apo-ACP to an active holo-ACP that plays a key role in fatty acids biosynthesis. Currently, the PPTase has been proved to be involved in the biosynthesis of polyunsaturated fatty acids (PUFAs) via a polyketide synthase (PKS) pathway in Thraustochytrids, while its characteristics are not clarified.ResultsHere, the heterologous PPTase gene (pfaE) from bacteria was first co-expressed with the PKS system (orfA–orfC) from Thraustochytrid Aurantiochytrium. Then, a new endogenous PPTase (ppt_a) in Aurantiochytrium was identified by homologous alignment and its function was verified in E. coli. Moreover, the endogenous ppt_a was then overexpressed in Aurantiochytrium, and results showed that the production and proportion of PUFAs, especially docosahexaenoic acid (DHA), in the transformant SD116::PPT_A were increased by 35.5% and 17.6%, respectively. Finally, higher DHA and PUFA proportion (53.9% and 64.5% of TFA, respectively) were obtained in SD116::PPT_A using a cerulenin feeding strategy.ConclusionsThis study has illustrated a PUFAs-synthase-specific PPTase in PKS system and provided a new strategy to improve the PUFA production in Thraustochytrids.

Highlights

Phosphopantetheinyl transferase (PPTase) can change the acyl-carrier protein (ACP) from an inactive apo-ACP to an active holo-ACP that plays a key role in fatty acids biosynthesis
The polyketide synthase (PKS) pathway is catalyzed by an enzyme complex, and the gene codings for the members of this complex are composed of three or four subunits and possess similar domain structures including β-ketoacyl synthase (KS), chain length factor (CLF), malonyl-CoA transacylase (MAT), acyl-carrier protein (ACP), ketoacyl reductase (KR), acyltransferase (AT), enoyl reductase (ER), and dehydratase (DH) domains (Fig. 1) [8, 12,13,14]
The PKS organization consists of three subunits OrfA, OrfB, and OrfC (Fig. 1)

Summary

Introduction

Phosphopantetheinyl transferase (PPTase) can change the acyl-carrier protein (ACP) from an inactive apo-ACP to an active holo-ACP that plays a key role in fatty acids biosynthesis. The PPTase has been proved to be involved in the biosynthesis of polyunsaturated fatty acids (PUFAs) via a polyketide synthase (PKS) pathway in Thraustochytrids, while its characteristics are not clarified. Polyunsaturated fatty acids (PUFAs), especially docosahexaenoic acid (DHA, 22:6 ω3) and eicosapentaenoic acid (EPA, 20:5 ω3), are rapidly gaining attention, due to their beneficial effects in the cognitive development. As it is known, PUFAs are synthesized by two pathways, the aerobic desaturase/elongase pathway and the. The putative PPTase encoding gene was identified in the Thraustochytrid species, such as Aurantiochytrium limacinum [20] and Hondaea fermentalgiana [7]; its characteristics are not clearly clarified

Methods

Results

Conclusion