Substrate specificity of catechol oxidase from Lycopus europaeus and characterization of the bioproducts of enzymic caffeic acid oxidation

The substrate specificity of catechol oxidase from Lycopus europaeus toward s phenols is examined. The enzyme catalyzes the oxidation of o-diphenols to o-quinones without hydroxylating monophenols, the additional activity of t yrosinase. Substrates containing a -COOH group are inhibitors for catechol oxidase, The products of enzymic oxidation of caffeic acid were analyzed an d isolated by HPLC with diode array detection. The neolignans of the 2,3-di hydro-1,4-benzodioxin type (3, 6-8), 6,7-dihydroxy-1-(3,4-dihydroxyphenyl)- 2,3-dicarboxy-1,2-dihydronaphthaline (1) 6,7-dihydroxy-1-(3,4-dihydroxyphen yl)-3-carboxynaphthaline (5) and 2,6-bis-(3',4'-dihydroxyphenyl)-1-carboxy- 3-oxacyclo-(3,0)-pentn-2-on-1-ene (4) were formed. A reaction mechanism for the formation of(ll 4 and 5) is discussed. (C) 1999 Federation of European Biochemical Societies.