Inhibitory effects of iron-based carbonaceous nanocomposites on mushroom tyrosinase activity: molecular aspects and mechanistic insights

Tyrosinase (Tyr) is a key enzyme in melanin biosynthesis, and its overexpression is related to several skin disorders, including melanomas and hyperpigmentation. Based on its relevant role, various molecules have been studied to control Tyr activity, but they usually present high toxicity and low outcomes. As an alternative, nanomaterials could be explored as inhibitors for Tyr due to their unique properties. In this work, small iron-containing carbon nanocomposites (FeCQDs, similar to 10 nm) were obtained without further passivation. The FeCQDs quench the mushroom Tyrosinase (mTyr) fluorescence following both static and dynamic mechanisms, and they bind very tightly to mTyr (K-s similar to 10(6) M-1), guided predominantly by hydrophobic interactions and hydrogen bonds. An increase in hydrophobicity of the aromatic microenvironment was observed due to the interaction of mTyr with FeCQDs. Besides the binding features, FeCQDs inhibit very efficiently the mTyr activity (IC50 = 163.9 +/- 4.9 nM) and behave as a non-competitive inhibitor. The determined IC50 for FeCQD is 110-fold lower than that of kojic acid. All of the presented results show the potential of metal-containing carbonaceous nanocomposites as efficient mTyr inhibitors.

Automated summary

In this study, small iron-containing carbon nanocomposites showed efficient inhibition of tyrosinase activity. They quenched the fluorescence of tyrosinase through both static and dynamic mechanisms and exhibited tight binding to the enzyme. The nanocomposites also behaved as non-competitive inhibitors, with an inhibition efficiency 110 times higher than kojic acid.