The inventors herein describe methods for the production of a functional human, animal, plant or microbe protein arrays and methods to assay for interactions between the proteins on the array with molecules of interest, for example, using such arrays to determine the in vitro metabolite profile of any drug. Such protein arrays can be used, for example, to assay, in a parallel fashion, the protein products of DNA sequences encoding drug metabolizing enzymes (DMES) to obtain a toxicology profile. Also described herein is a novel DME expression and purification strategy using detergents and not requiring an ultra-centrifugation step.