Plays a role in the biosynthesis of B-band O antigen for serotype O5. Catalyzes the amination of UDP-2-acetamido-2-deoxy-3-oxo-D-glucuronic acid (UDP-3-oxo-D-GlcNAcA) to UDP-2-acetamido-3-amino-2,3-dideoxy-D-glucuronic acid (UDP-GlcNAc3NA), using L-glutamate as the preferred amine donor. L-glutamate + UDP-2-acetamido-2-deoxy-alpha-D-ribo-hex-3-uluronate = 2-oxoglutarate + UDP-2-acetamido-3-amino-2,3-dideoxy-alpha-D-glucuronate Binds 1 pyridoxal phosphate per subunit. Optimum pH is 8.0 for the coupled WbpB/WbpE reaction. Optimum temperature is 30 degrees Celsius for the coupled WbpB/WbpE reaction. Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Homodimer. Belongs to the DegT/DnrJ/EryC1 family.