Biotransformation of docosahexaenoic acid into 10R,17S- dihydroxydocosahexaenoic acid as protectin Dx 10-epimer by serial reactions of arachidonate 8R- and 15S-lipoxygenases

Abstract Protectins, 10,17-dihydroxydocosahexaenoic acids (10,17-DiHDHAs), are belonged to specialized pro-resolving mediators (SPMs). Protectins are generated by polymorphonuclear leukocytes in humans and resolve inflammation and infection in trace amounts. However, the quantitative production of protectin Dx 10-epimer (10-epi PDX, 10R,17S-4Z,7Z,11E,13Z,15E,19Z-DiHDHA) has been not attempted to date. In this study, 10-epi PDX was quantitatively produced from docosahexaenoic acid (DHA) by serial whole-cell biotransformation of Escherichia coli expressing arachidonate (ARA) 8R-lipoxygenase (8R-LOX) from the coral Plexaura homomalla and E. coli expressing ARA 15S-LOX from the bacterium Archangium violaceum. The optimal bioconversion conditions to produce 10R-hydroxydocosahexaenoic acid (10R-HDHA) and 10-epi PDX were pH 8.0, 30°C, 2.0 mM DHA, and 4.0 g/L cells; and pH 8.5, 20°C, 1.4 mM 10R-HDHA, and 1.0 g/L cells, respectively. Under these optimized conditions, 2.0 mM (657 mg/L) DHA was converted into 1.2 mM (433 mg/L) 10-epi PDX via 1.4 mM (482 mg/L) 10R-HDHA by the serial whole-cell biotransformation within 90 min, with a molar conversion of 60% and volumetric productivity of 0.8 mM/h (288 mg/L/h). To the best of our knowledge, this is the first quantitative production of 10-epi PDX. Our results contribute to the efficient biocatalytic synthesis of SPMs.