Tyrosinase Kinetics: A Semi-quantitative Model of the Mechanism of Oxidation of Monohydric and Dihydric Phenolic Substrates

The phenylthiourea is a competitive inhibitor of the enzymatic oxidation of DOPA by phenoloxidase

“…Em and Eo forms with both copper ions in the oxidation state Cu(II) are the enzymatic forms that bind the substrate, DOPA [10][11][12][13][14] . In case of plant catecholoxidase, it has been shown that it is Cu(II)-CU(II) state of the enzyme that interacts with the PTU 35 .…”

“…This enzyme has three forms: "met" (with Cu(II)-Cu(II) in the active site), "deoxy"(Cu(I)-Cu(I)), and "oxy"(Cu(II)-O 2 -Cu(II)) 6,7 . Structural models for the active site of these three forms have been proposed [8][9][10][11][12][13][14] . PO catalyzes the initial steps of the melanization process, namely, the oxidation by molecular oxygen of monophenols (cresolase activity) and ortho-diphenols (catecholase activity) into the corresponding ortho-quinones.…”

Substrate-dependent kinetics in tyrosinase-based biosensing: amperometry vs. spectrophotometry

“…The monophenol oxidase reaction also depends on the presence of oxygen in the environment. Therefore, at high concentrations, the amount of phenol converted is limited by the amount of oxygen available in the assay [33,34]. This limits the highest analyte concentration that a tyrosinase biosensor can detect.…”

Identification of the immunodominant regions of the melanoma antigen tyrosinase by anti-tyrosinase monoclonal antibodies

“…In addition to above mentioned two reactions, tyrosinase has proposed to have third function of oxidation of 5,6-dihydroxyindole (DHI) to indolequinone (119). Tyrosinase is able to utilize tyrosine, DOPA and 5,6-dihydroxyindole (DHI) as substrates but in reality it is the hydroxylation of tyrosine that is the key, ratelimiting step (98). An example of the effect of a simple mutation in tyrosinase is seen in white (albino) mouse ( Figure 2).…”