Inhibitory Effects of a Palladium Complex on the Activity, Stability, and Structure of Tyrosinase Enzyme

denaturation of the tyrosinase with and without the presence of palladium complex. The tertiary and secondary structures of tyrosinase were detected by fluorescent and Circular Dichroism (CD) techniques. Results: The inhibition modes of palladium complex were competitive in both activities of the enzyme with Ki values of 3.74 and 10.55 μM for cresolase and catecholase activities, respectively. In thermal denaturation, the melting points (T m ) of the enzyme were 59.4˚C and 51˚C for the sole enzyme and its treatment by palladium, respectively. In chemical denaturation, the magnitudes of half denaturant concentration (C m ) were 1 μM vs. 1.36μM and the free energy of Gibss (ΔG H2O ) were calculated 9.3 vs. 7.5 kJ/M for the sole enzyme and its treatment by palladium, respectively. Conclusions: In overall the palladium complex acted as a good inhibitor of tyrosinase and induced the enzyme thermodynamic and conformational instability, therefore it can be considered in the hyper expression of tyrosinase in melanoma cancer.