Tyrosinase has been measured in homogenates of foreskins from newborn babies. The tyrosine hydroxylation reaction is dependent upon 3,4-dihydroxyphenylalanine as a cosubstrate, and the Km for tyrosine is 0.15 mM, similar to the value observed for other mammalian tyrosinases. The mean enzyme activity for black babies (n = 169) is about two and one-fourth times that for white babies (n = 82). For...

Finasteride is a well-known 5α-reductase inhibitor used for treatment of alopecia and prostate cancer. But the effect of finasteride in regulating melanogenesis is still unclear. In the present study the role of finasteride on melanogenesis was investigated. Finasteride decrease melanin level in melanocyte melan-a cells and B16F10 melanoma cells without inducing cytotoxicity. MC1R (melanocortin...

Tyrosinases are type 3 copper enzymes that are involved in the production of melanin and have two copper ions in the active site. Here, the crystallization and primary analysis of a tyrosinase from Bacillus megaterium is reported. The purified protein was crystallized in the absence or presence of zinc ions and the crystals diffracted to a resolution of 2.0 A. Crystals obtained in the presence ...

Phenoloxidases (POs) are a family of enzymes including tyrosinases, catecholases and laccases, which play an important role in immune defence mechanisms in various invertebrates. The aim of this study was to thoroughly identify the PO-like activity present in the hemolymph of the Pacific oyster Crassostrea gigas, by using different substrates (i.e. dopamine and p-phenylenediamine, PPD) and diff...

Latent phenoloxidase activity of hemocyanin (Hc) in whiteleg shrimp Penaeus vannamei was assayed to determine its potential involvement in postmortem melanosis. Conversion of pure 12-mer, but not 6-mer, hemocyanin to phenoloxidase by endogenous (serine proteinases) and exogenous (SDS) effectors demonstrated the need of complex aggregation for displaying enzyme activity. Because Hc was converted...

Cross-linking of β-casein by Trichoderma reesei tyrosinase (TrTyr) and Streptoverticillium mobaraense transglutaminase (Tgase) was analyzed by (31)P nuclear magnetic resonance (NMR) spectroscopy in ionic liquid (IL). According to (31)P NMR, 91% of the tyrosine side chains were cross-linked by TrTyr at high dosages. When Tgase was used, no changes were observed because a different cross-linking ...

The hydroxylation of tyrosine is an important reaction in the biosynthesis of many natural products. The use of bacteria for this reaction has not been very successful due to either the over-oxidation to ortho-quinone when using tyrosinases from bacteria or plants, or the lack of the native cofactor, tetrahydrobiopterin (BH4), needed for the activity of tyrosine hydroxylases (TH). Here, we demo...