The enzyme, characterized from the bacterium Pantoea agglomerans, is involved in biosynthesis of dapdiamide tripeptide antibiotics, a family of fumaramoyl- and epoxysuccinamoyl-peptides named for the presence of an (S)-2,3-diaminopropanoate (DAP) moiety and two amide linkages in their scaffold.
gene DdaF belongs to the dapdiamide antibiotic biosynthetic gene cluster. DdaF acts as a second ATP-dependent amide ligase, cleaving ATP to ADP and Pi during amide bond formation. DdaF adds Val, Ile, or Leu to the carboxylate of fumaramoyl-2,3-diaminopropionate to make the three dapdiamides A-C. To build the dapdiamide antibiotic scaffold, amidation must occur on the fumaroyl-diaminopropionate scaffold, after DdaG action but before DdaF catalysis
i.e. N-beta-epoxysuccinamoyl-2,3-diaminopropionate. DdaF can catalyze the ligation of both Nbeta-trans-epoxysuccinamoyl-diaminopropionate diastereomers to Val to produce the Nbeta-trans-epoxysuccinamoyl-diaminopropionate-L-valine dipeptide antibiotics. DdaF uses (R,R)-Nbeta-trans-epoxysuccinamoyl-diaminopropionate as a saturable substrate, whereas saturation is not achieved with (S,S)-Nbeta-trans-epoxysuccinamoyl-diaminopropionate at concentrations up to 590 microM
DdaF will not accept Nbeta-fumaroyl-diaminopropionate or Nalpha-fumaramoyl-diaminopropionate. The enzyme requires the fumaroyl moiety to be first converted to the fumaramoyl half amide in Nbeta-fumaramoyl-diaminopropionate