Characterization of 1-acyl-sn-glycerol-3-phosphate acyltransferase from a polyunsaturated fatty acid-producing bacterium, Shewanella livingstonensis Ac10

Abstract

Shewanella livingstonensis Ac10, a psychrotrophic bacterium, produces the omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA), as a fatty acyl chain of phospholipids at low temperatures. EPA is incorporated into the sn-2 position of phospholipids. 1-Acyl-sn-glycerol-3-phosphate acyltransferase (PlsC) catalyzes the acylation at the sn-2 position of 1-acyl-sn-glycerol-3-phosphate to form phosphatidic acid (PA). We found that 5 genes code for proteins homologous to Escherichia coli PlsC (named PlsC1 through PlsC5), suggesting that these PlsCs are involved in the synthesis of EPA-containing phospholipids. To examine the role of these putative PlsCs, we constructed the knockout mutants of each plsC gene (∆plsC1 to ∆plsC5). In the mutant ∆plsC1, the amount of phospholipids containing EPA was less. Functional expression studies in a temperature-sensitive mutant of PlsC, E. coli JC201, showed that PlsC1 has a PlsC activity with a broad acyl-coenzyme A (acyl-CoA) specificity including EPA-CoA. These results indicate that PlsC1 is a key enzyme in the synthesis of EPA-containing PA in S. livingstonensis Ac10.

Abbreviations: acyl-ACP, acyl-acyl carrier protein acyl-CoA, acyl-coenzyme A EPA, eicosapentaenoic acid ESI-MS, electrospray ionization-mass spectrometry LPA, 1-acyl-sn-glycerol-3-phosphate PA, phosphatidic acid PE, phosphatidylethanolamine PG, phosphatidylglycerol PlsC, 1-acyl-sn-glycerol-3-phosphate acyltransferase TLC, thin-layer chromatography