2.3. Tyrosinase activity assay

Tyrosinase activity was assayed as described.17 Briefly, cells were washed with phosphate‐buffered saline and homogenized in 20 mmol/L Tris/HCl (pH 7.5) containing 0.1% Triton X‐100 (Sigma‐Aldrich). Tyrosinase activity assayed as oxidation of L‐DOPA to DOPAchrome was monitored as follows. Cell extracts (100 μg/mL) were mixed with 100 μL freshly prepared substrate solution (0.1% L‐DOPA in phosphate‐buffered saline) and incubated 20 minutes at 37°C. DOPAchrome production was monitored by measuring absorbance at 490 nm using a plate reader (ARVO^™ X3).