Investigating β-Hydroxyenduracididine Formation in the Biosynthesis of the Mannopeptimycins

The mannopeptimycins (MPPs) are potent glycopeptide antibiotics that contain both D and L forms of the unique, arginine-derived amino acid β-hydroxyenduracididine (βhEnd). The product of the mppO gene in the MPP biosynthetic cluster resembles several non-heme iron, α-ketoglutarate-dependent oxygenases, such as VioC and clavaminate synthase. The role of MppO in βhEnd biosynthesis was confirmed through inactivation of mppO, which yielded a strain that produced dideoxy-MPPs, indicating that mppO is essential for generating the β-hydroxy functionality for both βhEnd residues. Characterization in vitro of recombinant His6-MppO expressed in E. coli revealed that MppO selectively hydroxylates the β carbon of free L-enduracididine.