The enzyme FabH, catalyzes the condensation of an acyl CoA with malonyl ACP (acyl carrier protein) to form a 3-ketoacyl ACP product.   This step represents the committed step of  fatty acid biosynthesis by dissociated fatty acid synthases.   The E. coli FabH is specific for straight short chain (C₂-C₃) acyl CoA substrates while the Streptomyces coelicolor FabH is able to process a broader range of straight and branched (C₂-C₇) acyl CoA substrates.  We have shown that altering FabH within an organism leads to predictable changes in the fatty acid profile.  We have also solved the structure of the Mycobacterium tuberculosis FabH which uses long (C₁₆ – C₂₂) acyl-CoA substrates.  This enzyme appears to play a role in the biosynthesis of the mycolic acid component of the cell wall.   Mutational, crystallographic, kinetic and inhibitor studies have been used to provide a dynamic mtFabH model which explains how these long chain substrates and products bind and release from the enzyme.   Finally we have shown that a FabH homolog, RedP, is also specific for straight short chain (C₂-C₃) acyl CoA substrates but plays a role initiating biosynthesis of red pigmented prodiginines in Streptomyces coelicolor.  These prodiginines have been shown to be effective in treatment of malaria infected mice.