Fig. 2From: Roles of the crotonyl-CoA carboxylase/reductase homologues in acetate assimilation and biosynthesis of immunosuppressant FK506 in Streptomyces tsukubaensis The structures of FK506 and FK520 differ only in the side chain moiety at the carbon C21. Incorporation of the allylmalonyl-CoA and ethylmalonyl-CoA extender unit analogue into the structure of FK506 is marked in the box Back to article page