The nylon oligomer biodegradation system of Flavobacterium and Pseudomonas

This review article is a compendium of the available information on the degradation of a man-made compound, 6-aminohexanoate-oligomer, in Flavobacterium and Pseudomonas strains, and discusses the molecular basis for adaptation of microorganisms toward these xenobiotic compounds. Three plasmid-encoded enzymes, 6-aminohexanoate-cyclic-dimer hydrolase (EI), 6-aminohexanoate-dimer hydrolase (EII), and endo-type 6-aminohexanoate-oligomer hydrolase (EIII) are responsible for the degradation of the oligomers. Two repeated sequences, designated RS-I and RS-II, are found on plasmid pOAD2, which is involved in 6-aminohexanoate degradation in Flavobacterium. RS-I appears 5 times on the pOAD2, and all copies have the same sequences as insertion sequence IS6100. RS-II appears twice on the plasmid. RS-IIA contains the gene encoding EII, while RS-IIB contains the gene for the analogous EII' protein. Both EII and EII' are polypeptides of 392 amino acids, which differ by 46 amino acid residues. The specific activity of the EII enzyme is 200-fold higher than that of EII'. Construction of various hybrid genes demonstrated that only the combination of two amino acid residues in the EII' enzyme can enhance the activity of the EII' to the same level as that of EII enzyme.