The KS3 family is the largest family in the KS system, with 14 subfamilies. KS3 enzymes are primarily produced in bacteria, with a small number of eukaryotes and archaea. KSs in this family contain KS domains present in both Type I FASs and the modular Type I of PKSs. While there are many slightly different enzymes in this family, the two most common 3-ketoacyl-ACP synthase I and synthase II.
