polyphenol oxidase (ppo), also known as tyrosinase (ec 1.14.18.1), is a copper-containing enzyme widely distributed in microorganisms, animals, and plants. this enzyme is responsible not only for browning in plants but also for melanization in animals. thus, tyrosinase inhibitors have a huge impact on industry and the economy. in the current study, we first purified the enzyme, then evaluated i...

Rosmarinic acid isolated from the Perilla frutescens (L.) was found to possess mushroom tyrosinase (EC 1.14.18.1) inhibitory activities with an IC50 of 4.0 μM. However, rosmarinic acid was oxidized as a substrate catalyzed by tyrosinase. The oxidation kinetics of mushroom tyrosinase by rosmarinic acid measured by spectrophotometic and polarographic methods showed Km=166.8 μM, 225.1 μM and Vmax=...

Surgical therapy for localized melanoma is highly successful. However, if melanoma spreads beyond its primary site, the results of treatment are poor. Therefore, early detection of circulating melanoma cells in the blood may be important. Currently, circulating melanoma cells are undetectable. Tyrosinase is an enzyme in the melanin synthetic pathway the expression of which is only found in mela...

The  inhibition effects seed and peel of melon on diphenolase activity of mashroom tyrosinase were investigated. The IC50 values and Ki values of seed and peel of melon were evaluated. increased the Km value and decreased the Vm value so it show mixed type inhibition on mushroom tyrosinase when L-DOPA was used as a substrate.

Many tyrosinase inhibitors have been alleged to have serious side effects. To search for relatively mild and safe tyrosinase inhibitors, two new 8-O-4′ neolignans, named huangnin A (1) and B (2), and four known analogs (3-6) were isolated from the seeds of Crataegus pinnatifida. Their structures were elucidated by spectroscopic analyses (1D, 2D NMR, HRESIMS, CD and Rh2(OCOCF3)4-induced CD). In ...

The reactivity of tyrosinase adsorbed on nanogold bound with 4,4'-bis(methanethiol)biphenyl monolayer self-assembled on a gold disk with catechol in a dipolar aprotic solvent, acetonitrile (AN), was studied by cyclic voltammetric and amperometric methods. Tyrosinase exhibited characteristics of a Michaelis-Menten kinetic mechanism. The tyrosinase attached to the nanogold continued to react with...

objective(s):involvement of tyrosinase in the synthesis of melanin and cell signaling pathway has made it an attractive target in the search for therapeutic inhibitors for treatment of different skin hyperpigmentation disorders and melanoma cancers. materials and methods: in the present study, we conducted a comprehensive kinetic analysis to understand the mechanisms of inhibition imposed by 2-...

For screening of skin-whitening ingredients that modulate inhibition of melanogenesis, tyrosinase promoter-based assay using a three-dimensional (3D) spheroid culture technique is a beneficial tool to improve the accuracy of raw material screening in cosmetics through mimicking of the in vivo microenvironment. Although the advantages of high-throughput screening (HTS) are widely known, there ha...

In this study, the authors investigated the anti-melanogenic effects of 3,8-dihydroxyquinoline (jineol) isolated from Scolopendra subspinipes mutilans, the mechanisms responsible for its inhibition of melanogenesis in melan-a cells, and its antioxidant efficacy. Mushroom tyrosinase activities and melanin contents were determined in melan-a cells, and the protein and mRNA levels of MITF, tyrosin...

ALTHOUGH it is easily demonstrated that when tyrosinase acts upon tyrosine 1-3:4-dihydroxyphenylalanine (dopa) is produced, it has hitherto not been clear why this is possible. Tyrosinase acts far more rapidly on dopa than on tyrosine, and dopa would therefore not be expected to accumulate in the reaction. However, from a mealworm tyrosinase-tyrosine reaction, which has proceeded 2-5 hr., dopa ...