Multistep Conversion of para-Substituted Phenols by Phenol Hydroxylase and 2,3-Dihydroxybiphenyl 1,2-Dioxygenase

A multistep conversion system of para-substituted phenols by recombinant phenol hydroxylase (PHIND) and 2,3-dihydroxybiphenyl 1,2-dioxygenase (BphC(LA-4)) was constructed in this study. Docking studies with different para-substituted phenols and corresponding catechols inside of the active site of PHIND and BphC(LA-4) predicted that all the substrates should be transformed. High-performance liquid chromatography-mass spectrometry analysis showed that the products of multistep conversion were the corresponding para-substituted catechols and semialdehydes. For the first-step conversion, the formation rate of 4-fluorocatechol (0.39 mu M/min/mg dry weight) by strain PHIND hydroxylation was 1.15, 6.50, 3.00, and 1.18-fold higher than the formation of 4-chlorocatechol, 4-bromocatechol, 4-nitrocatechol, and 4-methylcatechol, respectively. For the second-step conversion, the formation rates of semialdehydes by strain BphC(LA-4) were as follows: 5-fluoro-HODA > 5-chloro-HODA > 2-hydroxy-5-nitro-ODA > 5-bromo-HODA > 2-hydroxy-5-methyl-ODA. The present study suggested that the multistep conversion by both ring hydroxylase and cleavage dioxygenase should be potential in the synthesis of industrial precursors and provide a novel avenue in the wastewater recycling treatment.