High activity catechol 2,3-dioxygenase from the cresols - Degrading Stenotrophomonas maltophilia strain KB2

This study aimed at characterization of catechol 2,3-dioxygenase from Stenotrophomonas maltophilia KB2, being able to utilize a wide spectrum of aromatic substrates as a sole carbon and energy source. 2-methylphenol, 3-methylphenol, and 4-methylphenol was completely degraded during 24 h in concentration 6 mM, 7 mM, and 5 mM, respectively. When cells of strain KB2 were growing on methylphenols, catechol 2,3-dioxygenase was induced. Biochemical analysis revealed that the examined enzyme was similar to another catechol 2,3-dioxygenases, but showed extremely high activity. The enzyme was optimally active at 30 degrees C and pH 7.6. Kinetic studies showed that the value of K-m, V-max and Hill constant was 85.11 mu M 3.08 mu M min(-1) and 4.09 respectively. Comparative structural and phylogenetic analysis of catechol 2,3-dioxygenase from S. maltophilia KB2 had placed the protein with the single-ring substrate subfamily of the extradiol dioxygenase. We observed the presence of externally located alpha-helices and internally located beta-sheets. We also suggest that the Fe2+ ion binding is facilitated via four ligands: two histidine residues, one glutamate residue and one molecule of water. (C) 2011 Elsevier Ltd. All rights reserved.