Variations in IC50 Values with Purity of Mushroom Tyrosinase

Abstract

The effects of various inhibitors on crude, commercial and partially purified commercial mushroom tyrosinase were examined by comparing IC50 values. Kojic acid, salicylhydroxamic acid, tropolone, methimazole, and ammonium tetrathiomolybdate had relatively similar IC50 values for the crude, commercial and partially purified enzyme. 4-Hexylresorcinol seemed to have a somewhat higher IC50 value using crude extracts, compared to commercial or purified tyrosinase. Some inhibitors (NaCl, esculetin, biphenol, phloridzin) showed variations in IC50 values between the enzyme samples. In contrast, hydroquinone, lysozyme, Zn2+, and anisaldehyde showed little or no inhibition in concentration ranges reported to be effective inhibitors. Organic solvents (DMSO and ethanol) had IC50 values that were similar for some of the tyrosinase samples. Depending of the source of tyrosinase and choice of inhibitor, variations in IC50 values were observed.

Metal coordination and tyrosinase inhibition studies with Kojic-βAla-Kojic

“…IC 50 values for tyrosinase inhibitors can vary for a number of reasons, including choice of assay conditions, rate determinations, solvent considerations, and also the purity of the tyrosinase [38]. For instance, reported IC 50 values for kojic acid vary from 10 to 300 µM [38].…”

“…For instance, reported IC 50 values for kojic acid vary from 10 to 300 µM [38]. Under our experimental conditions the IC 50 value for KβAK was equal to 6.8±0.9 µM, whereas that of kojic acid was amounting to 35.4±4.3 µM.…”

Inhibitory effect of danazol on melanogenesis in mouse B16 melanoma cells

“…One unit of tyrosinase activity is defined as the total enzyme that catalyzes the formation of 1 µ mole of dopachrome in 1 min. The amount of dopachrome in the reaction was calculated using the LambertBeer Law while the molar extinction coefficient of dopachrome is 3600 M -1 ·cm -1 (Neeley et al, 2009). The specific tyrosinase activity was normalized with protein content in the reaction.…”

Afzelin positively regulates melanogenesis through the p38 MAPK pathway

“…Cellular tyrosinase activity was determined as described previously [21], with slight modifications. Briefly, human melanocytes were treated with afzelin, and the cells were washed twice with PBS and homogenized with 50 mM sodium phosphate (pH 6.8) buffer containing 1% Triton X-100 and 1 mM phenylmethanesulfonyl fluoride (PMSF) at 4 C with 30 repeated strokes in a Dounce homogenizer.…”