Phenol oxidase in Drosophila melanogaster occurs as prophenol oxidase A₃ and A₁, and is a copper-binding protein that oxygenizes catechols and catecholamines. Based on the primary structure of prophenol oxidase after purification, His residue ligates the two oxygen-binding copper atoms, Cu (II), at the active center. From nucleotide sequence, nucleotide substitution rates at codon positions, synonymous or nonsynonymous substitution rates, and codon usage parameters were analyzed.