Protein ligand interactions. Indole alkaloids as inhibitors for lactate dehydrogenase.

Kinetic analysis showed that the indole alkaloids strychnine and brucine interact competitively with the enzyme lactate dehydrogenase with respect to the substrate pyruvate and non competitively with respect to NADH. Since the alkaloids possess a potential enolate and a quaternary nitrogen they bridge the binding sites for the substrates - pyruvate and NAD+. Conformational alterations induced by the binding of ligands to the enzyme subunits are discussed in terms of the proposed chemical model.