Tyrosinase Lab Report

Introduction Tyrosinase is a copper-containing enzyme that catalyzes oxidation steps in melanin synthesis (Curto, et al.) Tyrosinase and its inhibitors have been studied for cosmetic and medical purposes. By inhibiting tyrosinase activity, skin can be whitened for cosmetic purposes. Inhibiting tyrosinase activity can also be a treatment for disorders involving elevated pigmentation of the skin such as age spots (Heng). Tyrosinase is active between a pH of 6.0 and 7.8. The optimal temperature for tyrosinase activity is 42° C, but the enzyme operates in the range of 25° C to 70° C (Kelly). Tyrosinases have two coupled enzymatic functions. One is cresolase activity, which catalyzes the hydroxylation of monophenols to form o-diphenols. The other enzymatic function is catecholase activity, which oxidizes o-phenols to produce o-quinones. O-quinones are highly reactive and typically polymerize to form melanin (Kelly, et al., Heng, et al). Tyrosinase is the most important enzyme in the melanin production pathway because it catalyzes the rate-limiting step. Tyrosinase is also thought to have other functions in melanin production (Tuskamoto).

However, in the presence of DOPA, the lag period should have been diminished enough to be negligible (Packer). If the lag period was present, though, the enzyme would have been less efficient in experiments done earlier, which is consistent the results. The results may also have been affected by the timing of the experiment because tyrosinase is only stable for approximately an hour under these reaction conditions (Heidcamp). It may not be accurate to base the reasons for the results entirely on benzoic acid acting as an inhibitor; the change in results may have also been because of decreased enzyme function. If fewer enzymes were functioning, the enzymes would have reached saturation sooner; this could have caused the decrease in