Removal of type 2 Cu from ascorbate oxidase and laccase by reaction with n,n-diethyldithiocarbamate

The type 2 Cu of ascorbate oxidase from zucchini peelings can be rapidly removed by reaction with a tenfold excess N,N-diethyldithiocarbamate (DDC) in air, while other chelating agents, such as EDTA, require anaerobic reducing conditions. The type 2 Cu of laccase from Rhus vernicifera is never removed under aerobic conditions. In anaerobiosis and in the presence of a reducing agent, EDTA is also unable to remove the copper unless a smaller lipophilic molecule (DDC or dimethylglyoxime) is present, acting as a mediator. Type 1 Cu is not involved in the reaction of ascorbate oxidase with DDC, but reduction of type 3 Cu is probably required for type 2 Cu depletion, suggesting interdependence of type 2 and type 3 copper. Type 2 Cu is less exposed in laccase, possibly because of the large carbohydrate content of this protein.