Catalyzes the NAD(P)H-dependent reductive condensation of alpha-ketoglutarate to the intermediate formed by the adjacently encoded enzyme PA4836, namely (2S)-2-amino-4-{[(1S)-1-carboxy-2-(1H-imidazol-4-yl)ethyl]amino}butanoate, leading to the production of pseudopaline. This is the last step in the biosynthesis of the metallophore pseudopaline, which is involved in the acquisition of nickel and zinc, and thus enables bacterial growth inside the host, where metal access is limited. Therefore, this enzyme probably contributes to Pseudomonas virulence. Can use neither pyruvate nor oxaloacetate in place of alpha-ketoglutarate. Is two-fold more efficient using NADPH than NADH as the electron donor