Kinetoplast metabolic enzymes
Gain and loss of metabolism-related genes within the
order of the Kinetoplastea.
For a detailed discussion of the metabolism of the Kinetoplastea see the blog by Fred Opperdoes
Events of gene loss and acquisition by lateral transfer are projected on a cladogram which depicts
the most likely course of kinetoplastid evolution. Only genes related to metabolism that have undergone
a change at a bifurcation are shown. These metabolic genes represent on average between 5 and 10% of the
total of genes present in each of the genomes analyzed.
For a list of all genes, either acquired or lost, and compiled in this gene tree click here
The topology of the above tree is based exclusively on the events of gain and loss of genes of metabolic enzymes.
At each bifurcation it reports the genes that were either acquired, by adaptation after duplication, or by events of
horizontal gene transfer, or that were lost, before or at the separation of two or more sister taxa. The placement of
the genera Trypanosoma, Phytomonas and Blechomonas within a single monophyletic group is based on the
observation that these trypanosomatids simultaneously lost the capacity to metabolize the amino acids isoleucine and
valine into the Krebs'-cycle intermediate succinate, as the result of a loss of the following three genes: propionyl-CoA
carboxylase, methylmalonyl-CoA epimerase and methylmalonyl-CoA mutase. The placement of the genera Leishmania,
Crithidia and Leptomonas within one monophyletic group is based on the following four observations: 1) all
Leishmaniinae have the capacity to oxidize the amino acids isoleucine, valine and methionine to succinate; 2) they all
acquired three genes of the heme biosynthesis pathway: i.e. protoporphyrinogen oxidase, coproporphyrinogen III oxidase
(although not in L. seymouri) and ferrochelatase; 3) they are the only trypanosomatids to have acquired several
urea-cycle enzymes such as arginase, argininosuccinate synthase (although not for L. major) and argininosuccinate
lyase; 4) they all have lost the capacity to oxidize leucine to acetyl-CoA, because of the loss of the HMGCoA lyase gene.
The placement of Paratrypanosoma confusum as the earliest branching trypanosomatid is based on the observation
that it is the only trypanosomatid to share with Bodo saltans an 'old' arginase gene as well as some genes
involved in histidine and tryptophan metabolism. These genes are not encountered in the other trypanosomatids, except
for Trypanosoma cruzi.
