Catalyzes the synthesis of GDP-perosamine from GDP-4-keto-6-deoxy-D-mannose and L-glutamate. Can use only L-glutamate as amino donor. 2-oxoglutarate + GDP-alpha-D-perosamine = GDP-4-dehydro-alpha-D-rhamnose + L-glutamate Divalent ions have no significant effect on activity. kcat is 18.98 sec(-1) for GDP-4-keto-6-deoxy-D-mannose. kcat is 10.41 sec(-1) for L-glutamate. Optimum pH is 7.5. Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Homodecamer. Mutant is deficient in expression of the O157 LPS antigen. Increases adherence to cultured epithelial cells. Belongs to the DegT/DnrJ/EryC1 family. Extended N-terminus.