Characterization of catechol 2,3-dioxygenase from Planococcus sp. strain S5 induced by high initial phenol concentration

Abstract

This study aimed at characterization of a new catechol 2,3-dioxygenase isolated from a Gram-positive bacteri-um able to utilize phenol as the sole carbon and energy source. Planococcus sp. strain S5 grown on 1 or 2 mM phenol showed activity of both a catechol 1,2- and cat-echol 2,3-dioxygenase while at a higher concentrations of phenol only catechol 2,3-dioxygenase activity was observed. The enzyme was optimally active at 60°C and pH 8.0. Kinetic studies showed that the Km and Vmax of the enzyme were 42.70 µM and 329.96 mU, respectively. The catechol 2,3-dioxygenase showed the following rela-tive meta-cleavage activities for various catechols tested: catechol (100%), 3-methylcatechol (13.67%), 4-meth-ylcatechol (106.33%) and 4-chlorocatechol (203.80%). The high reactivity of this enzyme towards 4-chlorocat-echol is different from that observed for other catechol 2,3-dioxygenases. Nucleotide sequencing and homology search revealed that the gene encoding the S5 catechol 2,3-dioxygenase shared the greatest homology with the known genes encoding isoenzymes from Gram-negative Pseudomonas strains.