Enzymatic carboxylation of hydroxystilbenes by the γ-resorcylic acid decarboxylase from Rhizobium radiobacter WU-0108 under reverse reaction conditions

We examined 66 aromatics for carboxylation by the γ-resorcylic acid decarboxylase from Rhizobium radiobacter WU-0108 under reverse reaction conditions. The enzyme carboxylated resorcinol, catechol, 5-methylresorcinol and three hydroxystilbenes (resveratrol, gnetol, and piceatannol) with high yields. Except for catechol, the structures of these substrates include a 1,3-dihydroxybenzene moiety. Other compounds gave no reaction products. The reaction products from resveratrol and gnetol were 2,6-dihydroxy-4-[(E)-2-(4-hydroxyphenyl)ethenyl]benzoic acid and 2,6-dihydroxy-4-[(E)-2-(2,6-dihydroxyphenyl)ethenyl]benzoic acid, respectively, as determined by mass spectrometry and nuclear magnetic resonance analyses. Kinetic analyses of the carboxylation reactions indicated that resveratrol and gnetol are better substrates than resorcinol or catechol.