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 intermedi ates. These electrophilic species are stereospecifically attacked by water to yield (R)-1-(4'-hydroxyphenyl) alcohols or rearranged in a competing rea ction to 1-(4'-hydroxyphenyl)alkenes. Here, we show that the product spectr um of VAO can be controlled by medium engineering. When the enzymatic conve rsion 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 to luene and acetonitrile and was dependent on the water activity of the react ion medium. A similar shift in alcohol/cis-alkene product ratio was observe d when the VAO-mediated conversion of 4-propylphenol was performed in the p resence of monovalent anions that bind specifically near the enzyme active site. (C) 2001 Federation of European Biochemical Societies. Published by E lsevier Science B.V. All rights reserved.