K-Casein Suppresses Melanogenesis in Cultured Pigment Cells

The effects of bovine milk proteins on melanogenesis in B16 cells were examined. Both whey protein isolate and casein exhibited depigmenting properties. Among the major protein components of milk—including β-lactoglobulin, α-lactalbumin, α-, β-, and k-casein—only K-casein exhibited the depigmenting effect. However, the carboxyl terminal peptide of K-casein, glycomacropeptide, did not show this activity. Also, K-casein promoted the proliferation of the cells and inhibited the activity of tyrosinase in the cells. These results indicate that K-casein acts as a melanogenesis-suppressing modulator.     

β-Lactoglobulin Suppresses Melanogenesis in Cultured Human Melanocytes

The effects of whey proteins from bovine milk on melanogenesis in cultured human melanocytes were examined. Among the major protein components of milk whey including β-lactoglobulin (BLG), α-lactalbumin, serum albumin, and IgG, only BLG exhibited the depigmenting effect at a concentration of 1 mg/ml. Also, BLG suppressed the activity of tyrosinase in these cells. Retinol, to which BLG is known to bind, slightly increased the pigmentation of the cells at concentrations in the range of 1–100 nM, and retinoic acid, a metabolite of retinol, exhibited a strong pigmentation-promoting effect within the same concentration range. Treatment of the cells with 1 mg/ml BLG completely abrogated the pigmentation induced by these A vitamins. These results demonstrate a novel biological activity of BLG and suggest that this activity is dependent on its ability to bind retinol.