Characterization of the 6-aminohexanoate-dimer hydrolase from Pseudomonas sp. NK87

Abstract

The DNA base sequence of the Pseudomonas sp. NK87 gene (P-nylB) for 6-aminohexanoate-dimer hydrolase (P-EII), a xenobiotic-compound-degrading enzyme, was determined. It has an open reading frame of 1188 bp, initiated by ATG and terminated by TAG, and coding for 396 amino acids. The base sequence of the open reading frame has 53 % sequence similarity to that of the gene for the same enzyme of Flavobacterium sp. K172 (F-nylB) and 35% sequence similarity with respect to the deduced amino acid sequence. The P-EII enzyme was purified from an Escherichia coli clone in which the P-EII gene was highly expressed. The P-EII enzyme was inhibited by a serine protease inhibitor, diisopropyl fluorophosphate, as was the F-EII enzyme. Double reciprocal plots obtained from various concentrations of daminohexanoate-dimer indicated that the kcat value of the P-EII enzyme (9.2 s-l) was approximately half that of the F-EII enzyme (19 s-'), and the P-EII enzyme had higher affinity toward this substrate (K, for P-EII, 0.6 mM; K, for F-EII, 15 mM). The P-EII enzyme had a temperature optimum of 48 "C, and a pH optimum of 7.5. It is speculated that since the P-nylB and F-nylB genes are more diverged from each other than the corresponding nylA genes, the latter may have evolved more recently.

Novel DNA Sequences from Natural Strains of the Nitrogen-Fixing Symbiotic Bacterium Sinorhizobium meliloti

“…strain NK87 (see Table S2 in the supplemental material). This protein was found capable of degrading nylon oligomers (19,34). Nylon oligomers are among the compounds not present in natural environments until they were synthesized and released by humans very recently.…”

“…Clone RDA-81 was homologous to a gene in Pseudomonas sp. strain NK87 that degrades nylon oligomers, a type of xenobiotic compound (19,34). Clone RDA-104 was homologous to a probable peptide synthetase gene in the symbiotic island of B. japonicum that may function in host specialization (16).…”

A review of biodegradation of synthetic plastic and foams

“…been extracted from fungi (45) and bacteria (46). Several studies related to the isolation, expression and transformation of genes encoding nylon degrading enzymes are reported in the literature (47,48). Reviews on nylon biodegradation have been provided by Negoro (49,50).…”

“…strain NK87. These enzymes have been named as P-EI and P-EII because they are capable of degrading similar nylon oligomers as are degraded by F-EI and F-EII (48,55). It has been proposed that F-EI degrades cyclic nylon dimer and F-EIII degrades cyclic nylon oligomers.…”

A plasmid encoding enzymes for nylon oligomer degradation: nucleotide sequence and analysis of pOAD2

“…Enzymes EI (P-EI) and EII (P-EII) in Pseudomonas sp. NK87 (P-ylA and P -y l B genes) are plasmid-encoded (Kanagawa e t al., 1989), and the amino acid sequence identities between F-EI and P-EI and between F-EII and P-EII are 99 YO and 35 %, respectively (Kanagawa et al, 1993;Tsuchiya et al, 1989).…”