This rapid multiplexing microplate kit is used to determine both the activity and quantity of cytochrome c oxidase in a mouse sample with greater speed and simplicity. The ratio of the two is a measure of specific activity. The COX enzyme is immunocaptured within the wells of the microplate and the activity is determined by following the oxidation of reduced Cytochrome c colorimetrically by the absorbance change at 550 nm. Subsequently, in these same wells the quantity of the enzyme can then be determined by adding a COX specific detector antibody and the appropriate alkaline phophatase conjugated antibody; this phosphatase changes a substrate from colorless to yellow at 405 nm. This reaction takes place in a time dependent manner proportional to the amount of protein captured in the wells. Included in this kit for performance of the multiplexing assay are buffers, detergent, substrates, and 96-well microplate with monoclonal antibody pre-bound to the wells of the plate, allowing for a stream-lined assay.