Characterization of the ornithine aminotransferase from Plasmodium falciparum

Mol Biochem Parasitol. 2001 Nov;118(1):1-10. doi: 10.1016/s0166-6851(01)00357-7.


The ornithine aminotransferase from Plasmodium falciparum 3D7 was cloned, functionally expressed, and characterized. The gene exists as a single copy in the malarial genome and is located on chromosomes 6/7/8. The deduced amino acid sequence was found to be 85% identical to a similar sequence discovered in Plasmodium yoelii, 82% identical to a partial sequence from Plasmodium vivax, and 42-53% identical to ornithine aminotransferases from other eukaryotes. The enzyme had a very narrow substrate specificity, and could only catalyze the transamination of alpha-ketoglutarate with ornithine or N-acetylornithine, and of glutamate-5-semialdehyde with glutamate and alanine. The aminooxy analogue of ornithine, canaline, was found to inhibit the ornithine aminotransferase uncompetatively with a Ki of 492+/-98 nM. As the enzyme effectively catalyzed both ornithine catabolism and formation, its potential role in ornithine biosynthesis from glutamine, via glutamate, glutamate-5-phosphate, and glutamate-5-semialdehyde, was examined. Over the course of a 3.5 h incubation, P. falciparum converted 34% of exogenous, radiolabeled glutamine to glutamate and 0.68% to ornithine. This low level of conversion suggests that the parasite may have alternative mechanisms for obtaining ornithine for polyamine biosynthesis.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Aminobutyrates / pharmacology
  • Animals
  • Erythrocytes / parasitology
  • Humans
  • Malaria, Falciparum / parasitology
  • Molecular Sequence Data
  • Ornithine / metabolism
  • Ornithine-Oxo-Acid Transaminase / chemistry
  • Ornithine-Oxo-Acid Transaminase / genetics
  • Ornithine-Oxo-Acid Transaminase / isolation & purification
  • Ornithine-Oxo-Acid Transaminase / metabolism*
  • Plasmodium falciparum / enzymology*
  • Plasmodium falciparum / genetics


  • Aminobutyrates
  • canaline
  • Ornithine
  • Ornithine-Oxo-Acid Transaminase

Associated data

  • GENBANK/AF249587