OXIDATIVE DECARBOXYLATIONS OF 4-HYDROXYMANDELIC ACID AND 2-(4-HYDROXYPHENYL)GLYCINE BY LACCASE FROM CORIOLUS-VERSICOLOR AND BILIRUBIN OXIDASES FROM TRACHYDERMA-TSUNODAE AND MYROTHECIUM-VERRUCARIA

Laccase from Coriolus versicolor and bilirubin oxidases from Trachyder ma tsunodae and Myrothecium verrucaria converted 4-hydroxymandelic aci d (HMA) and 2-(4-hydroxyphenyl)glycine into 4-hydroxy-benzaldehyde (HB A), which was a single product and was not converted further. The reac tions were oxidative decarboxylations that were considered to be cause d by the enzyme-catalyzed abstractions of hydrogen from the phenolic h ydroxyl groups. The decarboxylation of HMA was used for a new colorime tric measurement of the activities of these enzymes. One unit of the e nzymes was defined as the amount that catalyzed the formation of 1 mum ol of HBA per minute. When HMA was used for a substrate, the optimum p Hs of laccase, bilirubin oxidase from T. tsunodae, and bilirubin oxida se from M. verrucaria were 4.5, 5.0, and 8.5, respectively, and their K(m) values were 31.3 mM, 34.5 mM, and 22.3 mM, respectively.