Allyl Aryl Ether Cleavage by Blautia sp. MRG-PMF1 Cocorrinoid O-Demethylase

Abstract

Coabalamin-dependent O-demethylase in Blautia sp. strain MRG-PMF1 was found to catalyze the unprecedented allyl aryl ether cleavage reaction. To expand the potential biotechnological applications, the reaction mechanism of the allyl aryl ether C-O bond cleavage, proposed to utilize the reactive Co(I) supernucleophile species, was studied further from the anaerobic whole-cell biotransformation. Various allyl naphthyl ether derivatives were reacted with Blautia sp. MRG-PMF1 O-demethylase, and stereoisomers of allyl naphthyl ethers, including prenyl and but-2-enyl naphthyl ethers, were converted to the corresponding naphthol in a stereoselective manner. The allyl aryl ether cleavage reaction was regioselective, and 2-naphthyl ethers were converted faster than the corresponding 1-naphthyl ethers. However, MRG-PMF1 cocorrinoid O-demethylase was not able to convert (2-methylallyl) naphthyl ether substrates, and the conversion of propargyl naphthyl ether was extremely slow. From the results, it was proposed that the allyl ether cleavage reaction follows the nucleophilic conjugate substitution (S(N)2') mechanism. The reactivity and mechanism of the new allyl ether cleavage reaction by cobalamin-dependent O-demethylase would facilitate the application of Blautia sp. MRG-PMF1 O-demethylase in the area of green biotechnology. IMPORTANCE Biodegradation of environmental pollutants and valorization of biomaterials in a greener way is of great interest. Cobalamin-dependent O-demethylase in Blautia sp. MRG-PMF1 exclusively involves anaerobic C1 metabolism by cleaving the C-O bond of aromatic methoxy group and also produces various aryl alcohols by metabolizing allyl aryl ether compounds. Whereas methyl ether cleavage reaction is known to follow the S(N)2' mechanism, the reaction pattern and mechanism of the new allyl ether cleavage reaction by cobalamin-dependent O-demethylase have never been studied. For the first time, stereoselectivity and the S(N)2' mechanism of allyl aryl ether cleavage reaction by Blautia sp. MRG-PMF1 O-demethylase is reported, and the results would facilitate the application of Blautia sp. MRG-PMF1 O-demethylase in the area of green biotechnology.