Probing the modularity of megasynthases by rational engineering of a fatty acid synthase Type I.

Modularity is a fundamental property of megasynthases such as polyketide synthases (PKSs). In this study, we exploit the close resemblance between PKSs and animal fatty acid synthase (FAS) to re-engineer animal FAS to probe the modularity of the FAS/PKS family. Guided by sequence and structural information, we truncate and dissect animal FAS into its components, and reassemble them to generate new PKS-like modules as well as bimodular constructs. The novel re-engineered modules resemble all four common types of PKSs and demonstrate that this approach can be a powerful tool to deliver products with higher catalytic efficiency. Our data exemplify the inherent plasticity and robustness of the overall FAS/PKS fold, and open new avenues to explore FAS-based biosynthetic pathways for custom compound design.