The Syringate <i>O</i> -Demethylase Gene of <i>Sphingobium</i> sp. Strain SYK-6 Is Regulated by DesX, while Other Vanillate and Syringate Catabolism Genes Are Regulated by DesR
Takuma Araki, Kenta Tanatani, Naofumi Kamimura, Yuichiro Otsuka, Muneyoshi Yamaguchi, Masaya Nakamura, Eiji Masai
Abstract
Syringate is a major degradation product in the microbial and chemical degradation of syringyl lignin. Along with other low-molecular-weight aromatic compounds, syringate is produced by chemical lignin depolymerization. Converting this mixture into value-added chemicals using bacterial metabolism (i.e., biological funneling) is a promising option for lignin valorization. To construct an efficient microbial lignin conversion system, it is necessary to identify and characterize the genes involved in the uptake and catabolism of lignin-derived aromatic compounds and to elucidate their transcriptional regulation. In this study, we found that the transcription of desA , encoding syringate O -demethylase in SYK-6, is regulated by an IclR-type transcriptional regulator, DesX. The findings of this study, combined with our previous results on desR (encoding a MarR transcriptional regulator that controls the transcription of ligM and desB ), provide an overall picture of the transcriptional-regulatory systems for syringate and vanillate catabolism in SYK-6.