A BACTERIAL ENZYME DEGRADING THE MODEL LIGNIN COMPOUND BETA-ETHERASE IS A MEMBER OF THE GLUTATHIONE-S-TRANSFERASE SUPERFAMILY

Cleavage of beta-aryl ether linkages is essential in lignin degradatio n. We identified another beta-etherase gene (ligF), which contains an open reading frame of 771 bp and lies between genes coding Calpha-dehy drogenase (ligD) and beta-etherase (ligE). The beta-etherase activity of LigF expressed in Escherichia coli was more than 80 times as high a s that of LigE. ligF and ligE are homologous to glutathione-S-transfer ase, and upon addition of glutathione a remarkable acceleration of bet a-etherase activity was found in E. coli carrying ligF. It is conclude d that LigF plays a central role in beta-aryl ether cleavage and that glutathione is the hydrogen donor in this reaction.