Catalyzes the synthesis of GDP-perosamine from GDP-4-keto-6-deoxy-D-mannose and L-glutamate. Shows also weak activity with L-glutamine. 2-oxoglutarate + GDP-alpha-D-perosamine = GDP-4-dehydro-alpha-D-rhamnose + L-glutamate Optimum pH is 8.0. Bacterial outer membrane biogenesis; LPS O-antigen biosynthesis. Homotetramer. Belongs to the DegT/DnrJ/EryC1 family.