Funayama et al. [14] found that α-arbutin could not inhibit the diphenolase activity of MTYR, while β-arbutin could (IC50 was 8.4 mM), but as a TYR diphenolase inhibitor in B16 mouse melanoma cells, α-arbutin was 10 times more potent than β-arbutin. Here, PPIB is linked to melanoma.