Copper Oxidases in Thalli of the Liverwort Marchantia polymorpha

A study is presented on the properties of copper oxidases in thalli of the liverwort Marchantia polymorpha L. Catecholase and ascorbic acid oxidase are compared in their specific activity, reaction kinetics, inhibitor sensitivity and intracellular localization. It is shown that catecholase is predominantly bound to particulate cell fractions and is normally inhibited by the usual inactivators of copper enzymes. Ascorbic acid oxidase activity, on the other hand, is strongest in the soluble protein fraction and is quite resistant toward the same inhibitors at the pH-optimum of the enzyme. Both enzymes, when assayed with small tissue fragments, can be inhibited as expected.