Tuning of the product spectrum of vanillyl-alcohol oxidase by medium engineering

The flavoenzyme vanillyl-alcohol oxidase (VAO) catalyzes the conversion of 4-alkylphenols through the initial formation of p-quinone methide intermediates. These electrophilic species are stereospecifically attacked by water to yield (R)-1-(4'-hydroxyphenyl) alcohols or rearranged in a competing reaction to 1-(4'-hydroxyphenyl)alkenes. Here, we show that the product spectrum of VAO can be controlled by medium engineering. When the enzymatic conversion of 4-propylphenol was performed in organic solvent, the concentration of the alcohol decreased and the concentration of the cis-alkene, but not the trans-alkene, increased. This change in selectivity occurred in both toluene and acetonitrile and was dependent on the water activity of the reaction medium. A similar shift in alcohol/cis-alkene product ratio was observed when the VAO-mediated conversion of 4-propylphenol was performed in the presence of monovalent anions that bind specifically near the enzyme active site. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.