Related Experiment Video
Updated: Mar 1, 2026

Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
Thiosemicarbazones as inhibitors of tyrosinase enzyme
Mariana A Soares1, Mariana A Almeida1, Carla Marins-Goulart1
1Department of Chemistry, Universidade Federal Rural do Rio de Janeiro, Seropédica, RJ 23890-000, Brazil.
Abstract:
In the search for compounds which may inhibit the development of melanomas, a series of thiosemicarbazones has been investigated as possible inhibitors of the tyrosinase enzyme. The results showed that all the thiosemicarbazones tested exhibited significant inhibitory effects on the enzyme. Thiosemicarbazones Thio-1, Thio-2, Thio-3 and Thio-4 substituted with oxygenate moieties, were better inhibitors (IC50 0.42, 0.35, 0.36 and 0.44mM, respectively) than Thio-5, Thio-6, Thio-7 and Thio-8. For the better inhibitors, molecular docking results suggested that the oxygen present in the para position of the aromatic ring is essential for the tyrosinase inhibition, due its high ability for complexation with Cu2+ ions. Inside the active protein pocket, Thio-2 - the best studied inhibitor - is able to interact with the amino acid residues His-155, Gly-170 and Val-172 via hydrogen bonding and hydrophobic force. Thio-2, containing a substituent on the aromatic ring similar to the substrate l-DOPA, showed a competitive inhibition mechanism as viewed in a Lineweaver-Burk plot. The same results were observed in the UV-Vis curves.
Related Concept Videos
Enzyme Inhibition
The Electron Transport Chain
Inhibitors of the electron transport chain
Rotenone, a widely used pesticide, prevents electron transfer from Fe-S cluster to ubiquinone or Q...
Antihypertensive Drugs: Thiazide-Class Diuretics
Allosteric Proteins-ATCase
Aspartate transcarbamoylase (ATCase) is a cytosolic enzyme that catalyzes the condensation of L-aspartate and carbamoyl phosphate to N-carbamoyl-L-aspartate. This reaction is the first step in pyrimidine biosynthesis. UTP and CTP, the end products of the pyrimidine synthesis...
Preparation and Reactions of Sulfides
Inhibition of Cdk Activity

