Fatty Acyl-CoA Reductase and Wax Synthase from Euglena gracilis in the Biosynthesis of Medium-Chain Wax Esters

Euglena gracilis, a unicellular phytoflagellate, can accumulate a large amount of medium-chain wax esters under anaerobic growth conditions. Here we report the identification and characterization of two genes involved in the biosynthesis of wax esters in E. gracilis. The first gene encodes a fatty acyl-CoA reductase (EgFAR) involved in the conversion of fatty acyl-CoAs to fatty alcohols and the second gene codes for a wax synthase (EgWS) catalyzing esterification of fatty acyl-CoAs and fatty alcohols, yielding wax esters. When expressed in yeast (Saccharomyces cerevisiae), EgFAR converted myristic acid (14:0) and palmitic acid (16:0) to their corresponding alcohols (14:0Alc and 16:0Alc) with myristic acid as the preferred substrate. EgWS utilized a broad range of fatty acyl-CoAs and fatty alcohols as substrates with the preference towards myristic acid and palmitoleyl alcohol. The wax biosynthetic pathway was reconstituted by co-expressing EgFAR and EgWS in yeast. When myristic acid was fed to the yeast, myristyl myristate (14:0-14:0), myristyl palmitoleate (14:0-16:1), myristyl palmitate (14:0-16:0) and palmityl myristate (16:0-14:0) were produced. These results indicate EgFAR and EgWS are likely the two enzymes involved in the biosynthesis of medium-chain wax esters in E. gracilis.