Hydroxylates the beta carbon of free L-enduracididine to produce (3S)-3-hydroxy-L-enduracididine in biosynthesis of the nonproteinogenic amino acid beta-hydroxyenduracididine, a component of antibiotic mannopeptimycin. 2-oxoglutarate + L-enduracididine + O2 = (3S)-3-hydroxy-L-enduracididine + CO2 + succinate Binds 1 Fe(2+) ion per subunit. Antibiotic biosynthesis. Cells produce dideoxy-mannopeptimycins. Belongs to the clavaminate synthase family.