Thioester Bond Formation Catalyzed by CalO4: A β-Ketoacyl-ACP Synthase III-like Acyltransferase in Calicheamicin Biosynthesis.
A KAS III family enzyme, CalO4, is described that catalyzes C-S bond formation during the biosynthesis of the potent antitumor agent calicheamicin and provides a potential biocatalyst for hindered C-S bond formation and a target for engineering novel calicheamicin-like or other bioactive compounds.