The efficacy of ellagic acid (EA), one of the naturally occurring polyphenols, in inhibiting melanogenesis was examined in vitro and in vivo. When mushroom-derived tyrosinase, a metaloprotein containing copper, was incubated with EA, enzymatic activity tended to decrease with decreasing copper concentration. Enzyme activity partially recovered when copper was added to the inactivated enzyme. Tyrosinase activity in the B16 melanoma cells was observed to recover in a dose-dependent manner when copper ions were added to the medium containing EA. Based on these results, EA is thought to react specifically with the copper located at the active centre of the tyrosinase molecule. Furthermore, when EA was applied for 6 weeks to brownish guinea-pigs, which have melanocytes in their skin, at the same time as irradiating for 2 weeks with ultra-violet light, skin pigmentation was clearly suppressed and the skin to which EA had been applied showed features similar to that of non-irradiated skin. These areas were irradiated again when the application of EA had been completed, and skin pigmentation occurred at the former site of EA application. In similar studies with hydroquinone, re-pigmentation did not occur on the sites at which hydroquinone (1%) had been applied. Based on the results reported here, EA is thought to suppress melanogenesis by reacting with activated melanocytes and without injuring cells.

In the course of a search for an alkaline stable protease for industrial use, an alkaline protease (protease BYA) was isolated from an alkalophilic Bacillus sp. Y, and its properties were characterized. Its optimum pH was pH 10.0-12.5, when casein was used as a substrate. In addition to the stability of protease BYA at pH 6.5-13.0, it was also very stable towards various surface-active agents, such as sodium dodecyl sulfate and sodium linear alkylbenzene sulfonate. Protease BYA was most active at 70 degrees C. The isoelectric point (pI) of protease BYA was about 10.1. Protease BYA was characterized as a serine protease because of its sensitivity to phenylmethanesulfonyl fluoride and diisopropyl fluorophosphate. The protease seems to be related to proteases of the subtilisin family, such as subtilisin BPN', subtilisin Carlsberg, and No. 221 protease.

No abstract

The coat color of C57BL/6-Mitfvit/vit mice whitens with age, because of a one-nucleotide mutation in the DNA-binding region of the microphthalmia-associated transcription factor (MITF), which plays an important role in melanocyte growth and differentiation. To investigate the signals regulating MITF function, we prepared transgenic mice expressing three of the external signals that are important for melanocyte development, i.e., hepatocyte growth factor (HGF), stem cell factor (SCF), and endothelin-3 (ET3), and crossed these mice with Mitfvit/vit mice. We found that the age-dependent coat color whitening of the Mitfvit/vit mice was completely suppressed by the overexpression of HGF or SCF in the skin, but not by that of ET3. Moreover, HGF, but not ET3, promoted the proliferation of Mitfvit/vit mice-derived melanocytes in culture. These results suggest that the signals from exogenous HGF and SCF rescued the mi-vitiligo mutation and also that ET3 does not stimulate the common signal transduction pathway for MITF activation shared by HGF and SCF.

In the course of a search for an alkaline stable protease for industrial use, an alkaline protease (protease BYA) was isolated from an alkalophilic Bacillus sp. Y, and its properties were characterized. Its optimum pH was pH 10.0-12.5, when casein was used as a substrate. In addition to the stability of protease BYA at pH 6.5-13.0, it was also very stable towards various surface-active agents, such as sodium dodecyl sulfate and sodium linear alkylbenzene sulfonate. Protease BYA was most active at 70 degrees C. The isoelectric point (pI) of protease BYA was about 10.1. Protease BYA was characterized as a serine protease because of its sensitivity to phenylmethanesulfonyl fluoride and diisopropyl fluorophosphate. The protease seems to be related to proteases of the subtilisin family, such as subtilisin BPN', subtilisin Carlsberg, and No. 221 protease.