ИСТИНА

Lactate dehydrogenase A (LDHA) plays a significant role in the glucose metabolism of human cancer cells, thus constituting an attractive target for chemotherapy. The transition of the LDHA mobile loop 96-111 into the open conformation has been recently reported to be associated with forming an additional binding region. A hypothesized inhibitor occupying this site may prevent the binding with substrate pyruvate but not with the NADH coenzyme. This may be important for the design of selective inhibitors which exert no effect on the other NADH-dependent enzymes. Molecular models of the open conformation of LDHA have been constructed to enable the structure-based design of novel inhibitors, and the structural criteria for the selection of the most promising compounds were established. Superimposition of LDHA crystal structures with Swiss-PdbViewer 4.1.0 has shown that most amino acid residues are very flexible; however, the position of the Arg168 and His192 side chains, playing a key role in binding of substrates and inhibitors, remains fixed. Also, the side chain of the Thr247 residue was found to be in two possible conformations, differing by a 180 degree rotation. These three residues are located in the same active site region and can be targeted by a polar functional group of inhibitors. Two LDHA models were generated on the basis of the 4l4s crystal structure (complex with NADH), in which His192 was protonated (the first model) or deprotonated (the second model) accounting for its pKa = 7.3. An appropriate Thr247 side chain conformation was chosen to form hydrogen bond with putative inhibitors. Hydrogen atoms were added to the LDHA tetramer using Amber Tools 15, and then the energy minimization of the solvated system was performed to adjust the hydrogen positions using the Amber 14 package. Several known inhibitors were successfully docked into the active sites of the A- and B-subunits of the LDHA open form models with Lead Finder 1.1.16. Hydrogen bonds between the negative charged ligand’s group and the Arg168, His192, Thr247 residues were detected, which could be applied as criteria for structural filtration in the further virtual screening efforts. This work was supported by the Foundation for the Promotion of Innovations “UMNIK” (contract № 12449GU/2017).