Allosteric regulation of fungal fatty acid synthesis.

Mycobiota fatty acid synthases (FASs) catalyze iterative cycles of condensation, dehydration, and reduction to produce saturated fatty acids. Although these multienzymes are attractive antifungal drug targets, no clinically approved small-molecule inhibitors exist, and the regulation of de novo fatty acid synthesis remains poorly understood. Here, we identify an allosteric regulation of the FAS ketoacyl reduction reaction by palmitoyl-CoA. The palmitate moiety binds a distal site on the central wheel of fungal FAS from Saccharomyces cerevisiae and Candida albicans. This site also accommodates shorter acyl chains, but only palmitoyl-CoA suppresses ketoacyl reductase (KR) activity. While no major conformational changes occur in the reductase domain, palmitoyl-CoA binding quenches dynamics in the central disk, improving local resolution and stabilizing structured water molecules. This entropic effect underlies allosteric communication to the reductase site. Our findings uncover a regulatory mechanism of fungal FAS exploitable for antifungal drug design.