Reactions and significance of cytochrome P-450 enzymes

complex has a characteristic absorption maximum (Soret band) near 450 nm due to axial ligation with a cysteine thiolate of the protein (with or without substrate present). This cysteine residue is present in a relatively well conserved region, -80% into the protein from the N terminus. Collectively there are thousands of potential substrates for the P-450s; each of the P-450s may have a rather strict limitation of catalytic specificity