Vacuolar type H+ pumping pyrophosphatases of parasitic protozoa

Int J Parasitol. 2002 Jan;32(1):1-14. doi: 10.1016/s0020-7519(01)00325-3.

Abstract

Trans-membrane proton pumping is responsible for a myriad of physiological processes including the generation of proton motive force that drives bioenergetics. Among the various proton pumping enzymes, vacuolar pyrophosphatases (V-PPases) form a distinct class of proton pumps, which are characterised by their ability to translocate protons across a membrane by using the potential energy released by hydrolysis of the phosphoanhydride bond of inorganic pyrophosphate. Until recently, V-PPases were known to be the purview of only plant vacuoles and plasma membranes of phototrophic bacteria. Recent discoveries of V-PPases in kinetoplastid and apicomplexan parasites, however, have expanded our view of the evolutionary reach of these enzymes. The lack of V-PPases in the vertebrate hosts of these parasites makes them potentially excellent targets for developing broad-spectrum antiparasitic agents. This review surveys the current understanding of V-PPases in parasitic protozoa with an emphasis on malaria parasites. Topological predictions suggest remarkable similarity of the parasite enzymes to their plant homologues with 15-16 membrane spanning domains and conserved sequences shown to constitute critical catalytic residues. Remarkably, malaria parasites have been shown to possess two V-PPase genes, one is an apparent orthologue of the canonical plant enzyme, whereas the other is a more distantly related paralogue with homology to a recently identified new class of K+-insensitive plant V-PPases. V-PPases appear to localise both to the plasma membrane and cytoplasmic organelles believed to be acidocalcisomes or polyphosphate bodies. Gene transfer experiments suggest that one of the malarial V-PPases is predominantly localised to the surface of intraerythrocytic parasites. We suggest a model in which V-PPase localised to the malaria parasite plasma membrane may serve as an electrogenic pump utilising pyrophosphate as an energy source, thus sparing the more precious ATP. Searching for V-PPase inhibitors could prove fruitful as a novel means of antiparasitic chemotherapy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Membrane / enzymology
  • Cell Membrane / genetics
  • Leishmania donovani / enzymology*
  • Malaria / drug therapy
  • Molecular Sequence Data
  • Plasmodium / enzymology*
  • Plasmodium / genetics
  • Protein Conformation
  • Proton Pumps / chemistry
  • Proton Pumps / genetics
  • Proton Pumps / physiology*
  • Pyrophosphatases / chemistry
  • Pyrophosphatases / genetics
  • Pyrophosphatases / physiology*
  • Sequence Homology, Amino Acid
  • Toxoplasma / enzymology*
  • Trypanosoma / enzymology*
  • Vacuoles / enzymology

Substances

  • Proton Pumps
  • Pyrophosphatases