Involved in the biosynthesis of the siderophore enterobactin (enterochelin), which is a macrocyclic trimeric lactone of N-(2,3-dihydroxybenzoyl)-serine. EntF catalyzes the activation of L-serine via ATP-dependent PPi exchange reaction to form seryladenylate. Activated L-serine is loaded onto the peptidyl carrier domain via a thioester linkage to the phosphopanthetheine moiety, forming seryl-S-Ppant-EntF. EntF acts then as the sole catalyst for the formation of the three amide and three ester linkages found in enterobactin, using seryladenylate and 2,3-dihydroxybenzoate-S-Ppant-EntB (DHB-S-Ppant-EntB) as substrates, via the formation of a DHB-Ser-S-Ppant-EntF intermediate