Lactoperoxidase inhibition by tautomeric propylthiouracils

Lactoperoxidase (LPO) enzyme inhibition by tautomeric propylthiouracil (PTU) structures have been investigated in this work based on the in silico methodologies. Six possible PTU structures have been optimized to obtain their energy-minimized structures based on quantum mechanics computations. Afterwards, their interactions with LPO enzyme have been evaluated based on molecular docking simulations. The results indicated that the structural changes of PTU analogues could perturbate the interaction properties, in which it could be seen by either the magnitudes of binding energies or the types of interacting amino acids. In this work, the original thio-keto structure of PTU showed better interaction properties with LPO enzyme; however, the properties for other PTU derivatives have been deviated from this reference model. It is known that the tautomerism is common for biological structures; therefore, exploring their arisen effects on the structural properties and activities could reveal insightful information for judging their potency and efficacy.