The amino acid sequence of the enzyme coproporphyrinogen oxidase (copro'gen oxidase) in the heme biosynthetic pathway is known but its catalytic mechanism has yet to be determined. As a result, it is essential to carry out site-directed mutagenesis on highly conserved amino acids to help determine which amino acids are essential for catalysis. Often, a large number of mutants are created in this fashion, so it is in the researcher's best interest to have a technique to evaluate such mutants efficiently, quickly, and cheaply.