The assembly of monomeric human L-lactate dehydrogenase into catalytically active homotetramer is hindered by long-chain dicarboxylates

Prokaryotic and eukaryotic L-lactate dehydrogenases catalyze both the reduction of pyruvate to L-lactate and the reverse reaction generating the α-ketoacid. Remarkably, the energetic metabolism of human malignant cells is sustained by lactate dehydrogenase A (hLDH-A), the catalytic action of which is committed to its homotetrameric form (denoted hLDH-5), and is coupled to glycolysis. Therefore, hLDH-A represents a substantial druggable target, demanding the search for effective inhibitors of this enzyme. Here we report on the inhibition of hLDH-A exerted by dicarboxylates, whose performance is strictly dependent on their carbon chain length. In particular, the best performers were tetradecanedioic acid, hexadecanedioic acid, and crocetin (a polyunsaturated dicarboxylate), whose addition to assay mixtures strongly inhibited the activity of hLDH-A. Moreover, the inhibition of hLDH-A by hexadecanedioic acid was more effective against the monomeric enzyme than towards its tetrameric counterpart, suggesting that this dicarboxylate interferes with the assembly of hLDH-5. Furthermore, docking simulations support that long-, but not short-chain dicarboxylates, effectively bind to a specific site of monomeric hLDH-A, plausibly preventing its assembly into catalytically-competent hLDH-5. Overall, our observations indicate long-chain dicarboxylates as efficient inhibitors of hLDH-A, prompting to test their action in cellulo.