2-c-methylerythritol-4-phosphate and Tuberculosis

Tuberculosis remains a major infectious disease to humans. It accounts for approximately 8-9 million new cases worldwide and an estimated 1.6 million deaths annually. Effective treatments for tuberculosis consist of a combination of several drugs administered over long periods of time. Since Mycobacterium tuberculosis often acquires multiple drug resistant mechanisms, development of new drugs with innovative actions is urgently required. The 2C-methyl-D-erythritol 4-phosphate (MEP) pathway, in charge of the essential biosynthesis of isoprenoids, represents a promising and selective target for developing new drugs against tuberculosis. To date, only fosmidomycin, a molecule that targets the second enzyme of the MEP pathway, has reached clinical trials but recent advances elucidating the structure and kinetics of the MEP enzymes are likely to change this scenario. This review describes the structure, mechanism of action and inhibitors of the seven enzymes of the MEP pathway, with special attention to the reported studies in M. tuberculosis.

Topics: Aldose-Ketose Isomerases; Antitubercular Agents; Bacterial Proteins; Enzyme Inhibitors; Enzymes; Erythritol; Escherichia coli Proteins; Humans; Multienzyme Complexes; Mycobacterium tuberculosis; Oxidoreductases; Sugar Phosphates; Terpenes; Transferases; Tuberculosis

A number of pathogens, including the causative agents of tuberculosis and malaria, synthesize isopentenyl diphosphate via the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway rather than the classical mevalonate pathway found in humans. As part of a structure-based drug-discovery program against tuberculosis, IspD, the enzyme that carries out the third step in the MEP pathway, was targeted. Constructs of both the Mycobacterium smegmatis and the Mycobacterium tuberculosis enzymes that were suitable for structural and inhibitor-screening studies were engineered. Two crystal structures of the M. smegmatis enzyme were produced, one in complex with CTP and the other in complex with CMP. In addition, the M. tuberculosis enzyme was crystallized in complex with CTP. Here, the structure determination and crystallographic refinement of these crystal forms and the enzymatic characterization of the M. tuberculosis enzyme construct are reported. A comparison with known IspD structures allowed the definition of the structurally conserved core of the enzyme. It indicates potential flexibility in the enzyme and in particular in areas close to the active site. These well behaved constructs provide tools for future target-based screening of potential inhibitors. The conserved nature of the extended active site suggests that any new inhibitor will potentially exhibit broad-spectrum activity.

Topics: Amino Acid Sequence; Antitubercular Agents; Bacterial Proteins; Drug Design; Enzyme Inhibitors; Erythritol; Hemiterpenes; Humans; Molecular Sequence Data; Mycobacterium smegmatis; Mycobacterium tuberculosis; Organophosphorus Compounds; Sequence Alignment; Sugar Phosphates; Tuberculosis