Enhanced production of polyunsaturated fatty acids by enzyme engineering of tandem acyl carrier proteins

In some microorganisms, polyunsaturated fatty acids (PUFAs) are biosynthesized by PUFA synthases characterized by tandem acyl carrier proteins (ACPs) in subunit A. These ACPs were previously shown to be important for PUFA productivity. In this study, we examined their function in more detail. PUFA productivities increased depending on the number of ACPs without profile changes in each subunit A of eukaryotic and prokaryotic PUFA synthases. We also constructed derivative enzymes from subunit A with 5 x ACPs. Enzymes possessing one inactive ACP at any position produced similar to 30% PUFAs compared with the parental enzyme but unexpectedly had similar to 250% productivity compared with subunit A with 4 x ACPs. Enzymes constructed by replacing the 3rd ACP with an inactive ACP from another subunit A or ACP-unrelated sequences produced similar to 100% and similar to 3% PUFAs compared with the parental 3rd ACP-inactive enzyme, respectively. These results suggest that both the structure and number of ACP domains are important for PUFA productivity.