An Electron Spin Resonance Study of the State of Copper in Fungal Laccase

Abstract

THE work of Keilin and Mann¹ and of Tissières² conclusively demonstrated that laccase is a copper-protein enzyme. By analogy with the suggestion of Kubowitz³ in regard to polyphenoloxidase, it has generally been assumed that the enzyme contains Cu (II) in the resting state, and that catalytic activity is associated with a change in valency of the metal to Cu (I) (see, for example, ref. 4); but a direct study of this problem has never been made. Kertész⁵ has recently pointed out that Kubowitz's indirect method may give erroneous results, and he has, in fact, presented evidence that the metal in mushroom polyphenoloxidase is always in the Cu (I) state. The recent development of the electron spin resonance technique has made possible a more direct approach to this problem, and in the present communication we would like to present results of this technique which clearly show that fungal laccase contains Cu (II) which, during the oxidation of substrate, changes valency to Cu (I).