Amino acid alterations essential for increasing the catalytic activity of the nylon-oligomer-degradation enzyme of <em>Flavobacterium</em> sp.

The structural genes of two homologous enzymes, 6-aminohexanoate-dimer hydrolase (EII; nylB) and its evolutionally related protein EII&#39; (nylB&#39;) of Flavobacterium sp. KI72 have an open reading frame encoding a peptide of 392 amino acids, of which 47 are different, and conserved restriction sites. The specific activity of EII towards 6-aminohexanoate dimer is about 1000-fold that of EII&#39;. Construction of various hybrid genes obtained by exchanging fragments flanked by conserved restriction sites of the two genes demonstrated that two amino acid replacements in the EII&#39; enzyme, i.e. Gly181 → Asp (EII type) and His266 → Asn (EII type), enhanced the activity toward 6-aminohexanoate dimer 1000-fold. [ABSTRACT FROM AUTHOR]