The enzyme lactate dehydrogenase plays a key role in anaerobic glycolysis in normal cells and aerobic glycolysis (the Warburg effect) in cancer cells. Two isoenzymes exist (LDHA and B) and LDHA is widely regarded as a target for cancer drug development because of the role it plays in facilitating aerobic glycolysis. Numerous organic inhibitors of LDHA have been described but examples of organometallic inhibitors of LDHA are limited. Here, in silico modelling of a series of silver(I)-N-heterocyclic carbene (Ag-NHCs) ligands for use as inhibitors of lactate dehydrogenase enzyme has been described and compared to experimental LDHA enzyme kinetic results. The aim is to generate a model that can be used to design novel organometallic inhibitors of LDH that are potent and selective for either LDH A or B isoenzymes. Missing silver-containing bond and angle parameters required for molecular dynamics simulations were developed using quantum mechanics methods. Intramolecular interactions observed within the optimised structures are shown to be dependent on ligand chemical environment, with intramolecular hydrogen bonding and anion-π interactions influenced by choice of complexing halide, functional groups present in side chains, and chirality. In turn, these yielded a variety of silver-containing bond lengths and angles values, with their associated force constants varying similarly. Molecular dynamics simulations were conducted to determine the binding poses and dynamics of known potency Ag-NHCs within the known binding pockets of lactate dehydrogenase A (LDHA) isoenzyme. It has been shown that ligands containing one NHC ring (mono-NHC) preferably bound within the pyruvate substrate pocket, with those containing two rings (bis-NHC) preferably binding within the NADH cofactor pocket. In both cases, the binding of ligands induced significant conformational change, leading to non-competitive inhibition. Repeating these studies within lactate dehydrogenase B (LDHB) isoenzyme explored Ag-NHC isoenzyme specificity, with observed LDHA binding and mechanisms of action largely conserved, and therefore lacking isoenzyme specificity. Novel mono-NHC ligands have been studied, attempting to enhance binding and thus potential LDHA potencies. It was found that the use of carbonyl-containing side chains yielded potentially potent LDHA inhibitors, with extensions of ester molecular fragments successfully employed to develop ligands tailored to pyruvate binding pocket residues. Discussions of unexplored analogues highlighted the significant chemical space available for further development of highly potent LDHA inhibitors going forward.
| Date of Award | 14 Mar 2025 |
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| Original language | English |
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| Sponsors | Engineering and Physical Sciences Research Council |
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| Supervisor | David Cooke (Main Supervisor) & Roger Phillips (Co-Supervisor) |
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