Caffeic acid phenethyl ester (CAPE) is an ester of a hydroxycinnamic acid (phenylpropanoid) and a phenylethanoid (2-phenylethanol; 2-PE), which has long been used in traditional medicine. Here, we synthesized 54 hydroxycinnamic acid-phenylethanoid esters by feeding 64 combinations of hydroxycinnamic acids and phenylethanols to Escherichia coli harboring the rice genes OsPMT and Os4CL. The same approach was applied for ester synthesis with caffeic acid and eight different phenyl alcohols. Two hydroxycinnamoyl phenethyl esters, p-coumaroyl tyrosol and CAPE, were also synthesized from glucose using engineered E. coli by introducing genes for the synthesis of substrates. Consequently, we synthesized approximately 393.4 mg/L p-coumaroyl tyrosol and 23.8 mg/L CAPE with this approach. Overall, these findings demonstrate that the rice PMT and 4CL proteins can be used for the synthesis of diverse hydroxycinnamoyl phenylethanoid esters owing to their promiscuity and that further exploration of the biological activities of these compounds is warranted.
Keywords: caffeic acid phenethyl ester; hydroxycinnamic acids; metabolic engineering; phenylethanoids.