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B6db references: 11704268

type Journal Article
authors Gafan, C.; Wilson, J.; Berger, L.C.; Berger, B.J.
title Characterization of the ornithine aminotransferase from Plasmodium falciparum.
journal Mol Biochem Parasitol
Activity 2.6.1.13
Family 2.6.1.13
sel selected
ui 11704268
year (2001)
volume 118
number 1
pages 1-10
 
abstract 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.
last changed 2009/04/28 09:43

B6db references