Neospora caninum: Tachyzoites express a potent type-I nucleoside triphosphate hydrolase, but lack nucleoside diphosphate hydrolase activity

Takashi Asai, Daniel K. Howe, Kyoko Nakajima, Tomoyoshi Nozaki, Tsutomu Takeuchi, L. David Sibley

Research output: Contribution to journalArticle

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We have identified type I nucleoside triphosphate hydrolase (NTPase; EC activity, previously thought to be restricted to the virulent strains of Toxoplasma gondii, in the cell extracts of Neospora caninum tachyzoites. Sequence analysis of a complete cDNA from Nc-1 strain indicated that N. caninum NTPases shared approximately 69% identity to the NTPases of T. gondii and are most similar to the NTPase-I isozyme. Southern blot analysis of genomic DNA and sequence analysis of two independent NTP clones from the Nc-1 strain revealed the presence of multiple genes, at least two of which are transcribed. Substrate specificity and K(m) values for MgATP2 and MgADP- hydrolysis for recombinant or partially purified native NcNTPase were the same as those for the type I isozyme (NTPase-I). Significantly, no type II enzyme (NTPase-II) activity for NDP hydrolysis was detected in cell extracts of N. caninum, although it is universally present in all T. gondii strains that have been tested. This intriguing difference between these two closely related apicomplexan parasites may provide insight into the function of the NTPases during intracellular parasitism.

Original languageEnglish
Pages (from-to)277-285
Number of pages9
JournalExperimental Parasitology
Issue number3
Publication statusPublished - 1998 Nov



  • ATPase
  • Apicomplexan protozoa
  • Neosporosis
  • Purine salvage
  • Toxoplasma gondii

ASJC Scopus subject areas

  • Parasitology
  • Immunology
  • Infectious Diseases

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