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6 recordsLinked to original sources
PubMed1979

Conversion of dihydroorotate to orotate in parasitic protozoa.

The conversion of dihydroorotate to orotate, one of the key reactions in the de novo pyrimidine biosynthetic pathway, has been studied in a number of parasitic protozoa. Enzyme activities capable of carrying out this reaction were detected in six members of the Kinetoplastida (Trypanosoma brucei, Trypanosoma congolense, Trypanosoma vivax, Trypanosoma lewisi, Trypanosoma cruzi, Leishmania enriettii) and three members of the genus Plasmodium (P. knowlesi, P. berghei, P. gallinaceum). The mechanism of the reaction in the two groups of protozoa were quite distinct. In the Kinetoplastida, the enzyme is an hydroxylase which occurs in the soluble fraction of the cell and probably requires tetrahydrobiopterin for activity. In contrast, in Plasmodium, the enzyme is a dehydrogenase which is particulate, probably mitochondrial, and intimately connected to the electron transport chain to which it passes electrons directly, probably at the ubiquinone level. Neither activity is regulated by fully formed pyrimidines. The enzyme in Plasmodium is similar in mechanism to the isofunctional mammalian enzyme. However, since malarial ubiquinones are apparently different from those in the mammal and since menoctone, which is active in vivo in experimental malaria, is a good inhibitor of the malarial enzyme, it could represent a useful target for chemotherapeutic attack. The enzyme in the Kinetoplastida is quite distinct from that in the mammal so that it too apparently falls into this category, though none of the currently used antitrypanosomal drugs appears to block it activity at physiological concentrations.

Animals↗
PubMed1979

[Presence of genes of ribosomal and transfer RNAs in kinetoplast DNA from two Crithidia species].

The coding properties of kinetoplast DNA from two respresentatives of the order Kinetoplastidae--Crithidia oncopelti and C. fasciculata--were studied. Experiments on hybridization of the whole network and fraction of minicircles with labelled 23S and 16S rRNA and with tRNA isolated from kinetoplasts of C. oncopelti clearly demonstrated the presence of the genes for these RNAs in the whole network and their absence in the minicircles. It may be thus concluded that the genes of ribosomal and transfer RNAs are localized in the maxicircular molecules. Similar efficiency of hybridization of rRNAs from C. oncopelti with kDNA from C. fasciculata and C. oncopelti revealed significant conservativity of ribosomal genes in the protozoa under study.

Animals↗
PubMed2025

Expanding kinetoplastid genome annotation through protein structure comparison.

Kinetoplastids belong to the Discoba supergroup, an early divergent eukaryotic clade. Although the amount of genomic information on these parasites has grown substantially, assigning gene functions through traditional sequence-based homology methods remains challenging. Recently, significant advancements have been made in in-silico protein structure prediction and algorithms for rapid and precise large-scale protein structure comparisons. In this work, we developed a protein structure-based homology search pipeline (ASC, Annotation by Structural Comparisons) and applied it to transfer biological information to all kinetoplastid proteins available in TriTrypDB, the reference database for this lineage. Our pipeline enabled the assignment of structural similarity to a substantial portion of kinetoplastid proteins, improving current knowledge through annotation transfer. Additionally, we identified structural homologs for representatives of 6,700 uncharacterized proteins across 33 kinetoplastid species, proteins that could not be annotated using existing sequence-based tools and databases. As a result, this approach allowed us to infer potential biological information for a considerable number of kinetoplastid proteins. Among these, we identified structural homologs to ubiquitous eukaryotic proteins that are challenging to detect in kinetoplastid genomes through standard genome annotation pipelines. The results (KASC, Kinetoplastid Annotation by Structural Comparison) are openly accessible to the community at kasc.fcien.edu.uy through a user-friendly, gene-by-gene interface that enables visual inspection of the data.

Kinetoplastida↗