Meta-cleavage pathway of phenol degradation by Acinetobacter sp. strain AQ5NOL 1

Abstract

The characterization of bacterial enzymatic pathways of phenol metabolism is important to better understand phenol biodegradation. Phenol hydroxylase is the first enzyme involved in the oxidative metabolism of phenol, followed by further degradation via either meta- or ortho-pathways. In this study, the first known instance of phenol degradation via the meta-pathway by a member of the genus Acinetobacter (Acinetobacter sp. strain AQ5NOL 1) is reported. Phenol hydroxylase converts phenol to catechol, which is then converted via the meta-pathway to 2-hydroxymuconic semialdehyde by the catechol 2,3-dioxygenase enzyme. Phenol hydroxylase extracted from strain AQ5NOL 1 was fully purified using DEAE-Sepharose®, DEAE-Sephadex®, Q-Sepharose® and Zorbax® Bioseries GF-250 gel filtration and was demonstrated by SDS-PAGE to have a molecular weight of 50 kDa. The phenol hydroxylase was purified to about 210.51 fold. The optimum pH and temperature for enzyme activities are 20 °C and 7–7.5, respectively. The apparent K m and V max values of phenol hydroxylase with phenol as the substrate were 13.4 µM and 2.5 µmol min−1 mg−1, respectively. The enzyme was stable at −20 °C for 36 days.