Structural classification and properties of ketoacyl reductases, hydroxyacyl dehydratases and enoyl reductases.

Ketoacyl reductases (KRs), hydroxyacyl dehydratases (HDs) and enoyl reductases (ERs) are part of the fatty acid and polyketide synthesis cycles. Their reverse reactions, catalyzed by acyl dehydrogenases (equivalent to ERs), enoyl hydratases (equivalent to HDs) and hydroxyacyl dehydrogenases (equivalent to KRs), are part of fatty acid degradation by β-oxidation. These enzymes have been classified into families based on similarities in their primary and tertiary structures, and these families and their structures are included in the ThYme (Thioester-active enzYmes) database. Members of each family have strong sequence similarity and have essentially the same tertiary structure, mechanism and catalytic residues.