Biological oxidation of manganese (Mn) contributes significantly to naturally occurring Mn oxides and Mn cycling in the environment. The organisms, enzymes, and mechanisms by which biological Mn oxidation occurs is an active area of study.1 The reasons for the biotic Mn oxidation phenomenon and the enzymes that catalyze it are not entirely clear. Certain multicopper oxidases (MCOs) isolated from bacteria have been shown to oxidize Mn and are therefore a focus of study.2 We previously designed a model of non-coupled dinuclear copper enzymes into the azurin protein scaffolding.3 We employed this designed copper enzyme, with type 1 and type 2 copper centers, as a model MCO and examined its ability to oxidize Mn(II) using the leucoberbelin blue assay as a colorimetric detector of oxidized Mn species. Applying a peroxide shunt, our copper enzyme was found to oxidize Mn(II) to insoluble Mn(IV) species at rates rivaling cultures of the known bacterial Mn oxidizer, Pseudomonas putida. To further understand this activity, we examined different variants of the azurin model protein and used different metal ion loadings. Our data shows that the di-copper version of the azurin model was active at oxidizing Mn while a single Type 2 copper center showed even higher activity. The latest assay data, along with control reactions and EPR studies of the reactants and products will be presented. An understanding of the oxidation of Mn by copper enzyme systems can lead to further understanding of Mn oxidation by microorganisms.