Pseudomonas putida ATCC 17453 grew with either (+)- or (-)-camphor as sole carbon source. Enantiomer-specific 'biological Baeyer-Villiger' monooxygenases were synthesized irrespective of the camphor isomer used for growth. The two enzymes are probably the products of separate genes but showed many similarities. Each consisted of two electrophoretically identical subunits, bound flavin mononucleotide (FMN) non-covalently and accepted electrons from an induced NADH dehydrogenase which interacted with the FMN bound to the oxygenating component. They showed minor differences in M(r) with 3,6-diketocamphane 1,6-monooxygenase being the smaller enzyme. Isoelectric focussing showed the two enzymes to have different acidic pI values. Polyclonal antibodies raised against 3,6-diketocamphane 1,6-monooxygenase also cross-reacted with 2,5-diketocamphane 1,2-monooxygenase and its subunits.