Oxidative biodegradation of 4-chlorophenol by using recombinant monooxygenase cloned and overexpressed from Arthrobacter chlorophenolicus A6

- Arthrobacter chlorophenolicus A6 possesses DNA genes for 4-chlorophenol degradation.
- Soluble form CphC-I was expressed, whereas CphB expressed in an insoluble form.
- CphC-I exhibited high specific activity when coupled with a flavin reductase, Fre.
- vmax = 223.3 μM·min−1, KM = 249.4 μM, and kcat/KM = 0.052 min−1·μM−1.

In this study, cphC-I and cphB, encoding a putative two-component flavin-diffusible monooxygenase (TC-FDM) complex, were cloned from Arthrobacter chlorophenolicus A6. The corresponding enzymes were overexpressed to assess the feasibility of their utilization for the oxidative decomposition of 4-chlorophenol (4-CP). Soluble CphC-I was produced at a high level (∼50%), and subsequently purified. Since CphB was expressed in an insoluble form, a flavin reductase, Fre, cloned from Escherichia coli was used as an alternative reductase. CphC-I utilized cofactor FADH2, which was reduced by Fre for the hydroxylation of 4-CP. This recombinant enzyme complex exhibited a higher specific activity for the oxidation of 4-CP (45.34 U/mg-protein) than that exhibited by CphC-I contained in cells (0.18 U/mg-protein). The Michaelis-Menten kinetic parameters were determined as: vmax = 223.3 μM·min−1, KM = 249.4 μM, and kcat/KM = 0.052 min−1·μM−1. These results could be useful for the development of a new biochemical remediation technique based on enzymatic agents catalyzing the degradation of phenolic contaminants.

Color change from yellow to orange-red after 4-CP degradation by CphC-I. CphC-I concentration from 0.1 to 25 μM from left to right.123