Functions of aldolase in lipid synthesis of Schizochytrium sp. by gene disruption to switch carbon metabolism

Abstract

Background As a key rate-limiting enzyme in the glycolytic pathway of cells, aldolase affects the distribution of intracellular carbon flux and determines the overall ability of subsequent cell metabolism, which are mainly reported in the medical related researches, but rarely involved microorganisms. In this study, the aldolase gene of Schizochytrium limacinum SR21 (ALDOA) was knocked out to explore the effect of regulating carbon flux on cell growth and lipid synthesis. Results The knockout of ALDOA showed an adverse effect on cell growth and total lipids production, which was decreased by 9.6% and 23.2%, respectively, but helped to improve the synthetic ability of polyunsaturated fatty acids (PUFAs), in which the proportion of docosahexaenoic acid (DHA) increased by 22.9%. Analysis of phospholipomics, real-time quantitative PCR and metabolomics revealed that the knockout of ALDOA weakened the glycolysis pathway and tricarboxylic acid cycle to inhibit cell growth, and lowered the Kennedy pathway to reduce the production of total lipids and the synthesis of phospholipids to affect cell metabolism. Correspondingly, the knockout of ALDOA enhanced the metabolic flux of the pentose phosphate pathway to provide more reducing power for PUFAs accumulation and improved the glycerophosphorylcholine acylation pathway to promote the accumulation of DHA. Conclusions ALDOA knockout redistributes the carbon metabolic flux in cells, by weakening the glycolysis, tricarboxylic acid cycle and glyceride synthesis pathway to inhibit cell growth and total lipid production, and strengthening the pentose phosphate pathway and glycerophosphorylcholine acylation pathway to increase the synthesis of PUFAs and DHA accumulation. This study provides a new idea for identifying the aldolase function in microorganisms and a metabolic strategy to improve DHA accumulation in Schizochytrium.