Molecular cloning of the nahC gene encoding 1,2-dihydroxynaphthalene dioxygenase from Pseudomonas fluorescens

초록

The complete nucleotide sequence of the nahC gene from Pseudomonas fluorescens, the structural gene for 1,2-dihydroxynaphthalene (1,2-DHN) dioxygenase, was determined. The 1,2-DHN dioxygenase is an extradiol ring-cleavage enzyme that cleaves the first ring of 1,2-dihydroxynaphthalene. The amino acid sequence of the dioxygenase deduced from the nucleotide sequence suggested that the holoenzyme consists of eight identical subunits with a molecular weight of approximately 34,200. The amino acid sequence of 1,2-DHN dioxygenase showed more than 90% homology with those of the dioxygenases of other Pseudomonas strains. However, sequence similarity with those of the Sphingomonas species was less than 60%. The nahC gene of P. fluorescens was moderately expressed in E. coli NM522, as determined by enzymatic activity.

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