Leishmania pyruvate kinase: the crystal structure reveals the structural basis of its unique regulatory properties.

Glycolysis occupies a central role in cellular metabolism, and is of particular importance for the catabolic production of ATP in protozoan parasites such as Leishmania and Trypanosoma. In these organisms pyruvate kinase plays a key regulatory role, and is unique in responding to fructose 2,6-bisphosphate as allosteric activator. The determination of the crystal structure of the first eukaryotic pyruvate kinase in the T-state (the inactive or 'tense' conformation of allosteric enzymes) is described. A comparison of the effector sites of the Leishmania and yeast enzymes reveals the structural basis for the different effector specificity. Two loops, comprising residues 443-453 and 480-489, adopt very different conformations in the two enzymes, and Lys-453 and His-480 that are a feature of trypanosomatid enzymes provide probable ligands for the 2-phospho group of the effector molecule. These and other differences offer an opportunity for the design of drugs that would exploit regulatory differences between parasite and host.