Kanagawa K, Oishi M, Negoro S, Urabe I, Okada H
Department of Biotechnology, Osaka University, Japan.
J Gen Microbiol. 1993 Apr;139(4):787-95. doi: 10.1099/00221287-139-4-787.
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. KI72 (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 6-aminohexanoate-dimer indicated that the kcat value of the P-EII enzyme (9.2 s-1) was approximately half that of the F-EII enzyme (19 s-1), and the P-EII enzyme had higher affinity toward this substrate (Km for P-EII, 0.6 mM; Km for F-EII, 15 mM). The P-EII enzyme had a temperature optimum of 48 degrees 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.
测定了用于降解异生物质化合物的6-氨基己酸二聚体水解酶（P-EII）的假单胞菌属NK87基因（P-nylB）的DNA碱基序列。它有一个1188 bp的开放阅读框，由ATG起始，TAG终止，编码396个氨基酸。该开放阅读框的碱基序列与黄杆菌属KI72（F-nylB）中相同酶的基因序列相似度为53%，与推导的氨基酸序列的相似度为35%。P-EII酶是从一个P-EII基因高表达的大肠杆菌克隆中纯化得到的。P-EII酶和F-EII酶一样，受到丝氨酸蛋白酶抑制剂二异丙基氟磷酸的抑制。从不同浓度的6-氨基己酸二聚体得到的双倒数图表明，P-EII酶的kcat值（9.2 s-1）约为F-EII酶（19 s-1）的一半，且P-EII酶对该底物具有更高的亲和力（P-EII的Km为0.6 mM；F-EII的Km为15 mM）。P-EII酶的最适温度为48℃，最适pH为7.5。据推测，由于P-nylB和F-nylB基因彼此之间的差异比相应的nylA基因更大，后者可能是最近才进化出来的。
