Parasite mitochondria as drug target: diversity and dynamic changes during the life cycle.
Parasites have developed a wide variety of physiological functions to survive within the specialized environments of the host. Regarding energy metabolism, which represents an essential factor for survival, parasites adapt low oxygen tension in host mammals using metabolic systems that differ substantially from those of the host. Most parasites do not use free oxygen available within the host, but employ systems other than oxidative phosphorylation for ATP synthesis. Furthermore, parasites display marked changes in mitochondrial morphology and components during the life cycle, and these represent very interesting elements of biological processes such as developmental control and environmental adaptation. The enzymes in parasite-specific pathways offer potential targets for chemotherapy. Cyanide-insensitive trypanosome alternative oxidase (TAO) is the terminal oxidase of the respiratory chain of long slender bloodstream forms of the African trypanosome, which causes sleeping sickness. Recently, the most potent inhibitor of TAO to date, ascofuranone, was isolated from the phytopathogenic fungus, Ascochyta visiae. The inhibitory mechanisms of ascofuranone have been revealed using recombinant enzyme. Parasite-specific respiratory systems are also found in helminths. The NADH-fumarate reductase system in mitochondria form a final step in the phosphoenolpyruvate carboxykinase (PEPCK)-succinate pathway, which plays an important role in anaerobic energy metabolism for the Ascaris suum adult. Enzymes in this system, such as NADH-rhodoquinone reductase (complex I) and rhodoquinol-fumarate reductase (complex II), form promising targets for chemotherapy. In fact, a specific inhibitor of nematode complex I, nafuredin, has been found in mass-screening using parasite mitochondria.
Kita
Kiyoshi
K
Department of Biomedical Chemistry, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. kitak@m.u-tokyo.ac.jp
Nihei
Coichi
C
Tomitsuka
Eriko
E
D000595:Amino Acid Sequence; D000818:Animals; D000977:Antiparasitic Agents / Q000494:pharmacology*; D017165:Ascaris suum / Q000254:growth & development / Q000378:metabolism; D004734:Energy Metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008018:Life Cycle Stages; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010088:Oxidoreductases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012717:Sesquiterpenes / Q000737:chemistry / Q000494:pharmacology; D014346:Trypanosoma brucei brucei / Q000201:enzymology
D000977:Antiparasitic Agents; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D012717:Sesquiterpenes; D010088:Oxidoreductases; C006640:ascofuranone