Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024530 (malaria)
 44,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dihydroorotate dehydrogenase (DHODase) has been purified 400-fold from the rodent malaria parasite Plasmodium berghei to apparent homogeneity by Triton X-100 solubilization followed by anion-exchange, Cibacron Blue F3GA-agarose affinity, and gel filtration chromatography. The purified enzyme has a molecular mass of 52 +/- 2 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and of 55 +/- 6 kDa by gel filtration chromatography, and it has a pI of 8.2. It is active in monomeric form, contains 2.022 mol of iron and 1.602 acid-labile sulfurs per mole of enzyme, and does not contain a flavin cofactor. The purified DHODase exhibits optimal activity at pH 8.0 in the presence of the ubiquinone coenzyme CoQ6, CoQ7, CoQ9, or CoQ10. The Km values for L-DHO and CoQ6 are 7.9 +/- 2.5 microM and 21.6 +/- 5.5 microM, respectively. The kcat values for both substrates are 11.44 min-1 and 11.70 min-1, respectively. The reaction product orotate and an orotate analogue, 5-fluoroorotate, are competitive inhibitors of the enzyme-catalyzed reaction with Ki values of 30.5 microM and 34.9 microM, respectively. The requirement of the long-chain ubiquinones for activity supports the hypothesis of the linkage of pyrimidine biosynthesis to the electron transport system and oxygen utilization in malaria by DHODase via ubiquinones [Gutteridge, W. E., Dave, D., & Richards, W. H. G. (1979) Biochim. Biophys. Acta 582, 390-401].
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PMID:Purification and characterization of dihydroorotate dehydrogenase from the rodent malaria parasite Plasmodium berghei. 184 78

The mitochondrial dihydroorotate dehydrogenase (DHODase), the single redox reaction in the pyrimidine de novo synthetic pathway, was purified to near homogeneity by detergent solubilization and fast protein liquid chromatography (FPLC) techniques from the mature trophozoites and schizonts of Plasmodium falciparum, human malaria parasite. The purified DHODase was monofunctional protein with a M(r) of 56,000 +/- 4000, based on Superose 12 gel filtration FPLC and SDS-PAGE analyses. Polyclonal antibodies raised against the purified P. falciparum protein was cross-reacted with P. berghei, rodent malaria parasite. The optimal activity of DHODase required long chain of coenzyme Q (CoQ6-10) which were essential for electron transfer. The Km and kcat values for L-dihydroorotate were 14.4 +/- 5.9 microM and 15.0 +/- 1.4 min-1, respectively; for CoQ6, they were 22.5 +/- 6.4 microM and 21.6 +/- 3.4 min-1. L-Orotate, an enzymatic product, was a strong competitive inhibitor with Ki of 18.2 +/- 3.6 microM. The 5-substituted L-orotates having antimalarial activities against P. falciparum in vitro were found to be competitive inhibitors. The inhibitory effect by these 5-substituted L-orotates on the malarial DHODase was different from the mammalian enzyme. Various benzoquinones and naphthoquinones were found to inhibit the purified DHODase activity at a different degree. Mitochondria from erythrocytic cycle of P. falciparum were purified, using differential centrifugation and followed by Percoll density gradient separation, with purifications of 13-fold and overall yields of 33%. The double-membraned mitochondria had a few tubular-like cristae structure as what found in many protozoan parasites. DHODase was localized inside the mitochondria as probed by immunogold labeling with the polyclonal antibodies and selective solubilization by digitonin.
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PMID:Purification, characterization and localization of mitochondrial dihydroorotate dehydrogenase in Plasmodium falciparum, human malaria parasite. 772 9