Speaker Paul Michels
Title The origin of glycolysis in peroxisomes (glycosomes) of trypanosomes
Date February 25, 2003
Time & Location 16:00-17:00 h, FALW - Boelelaan 1085 - M212
Host Barbara Bakker (barbara.bakker@falw.vu.nl)

Abstract
An unique feature of Kinetoplastida (the protozoan order comprising trypanosomes) is the compartmentation of glycolysis within peroxisome-like organelles called glycosomes.  Our original hypothesis that the glycosome was derived from a bacterial endosymbiont did not find much support through the initial analyses of glycosomal matrix-protein sequences that we determined.  Moreover, protein import into peroxisomes and glycosomes appeared unrelated to that of any protein translocation mechanism known in prokaryotes. In recent years, gene sequences have become available for a large number of organisms representative of all major taxa.  This enabled us to investigate thoroughly the phylogenetic relationships of trypanosomatid metabolic enzymes with their homologues from many organisms.  Surprisingly, a considerable number of parasite enzymes appear mostly related to enzymes from phototrophic organisms; either enzymes from plants/algae cytosolic or plastidic- or from cyanobacteria.  This holds true for several enzymes of the glycolytic and pentosephosphate pathways and various other enzymes.  Moreover, Trypanosomatidae appear to share some other features with plants.  Intriguingly, we detected a sedoheptulose-1,7-bisphosphatase, considered a hallmark of the Calvin cycle of photosynthetic organisms.  Together these data suggest that ancestral Kinetoplastida must have harbored a phototrophic endosymbiont.  This endosymbiont (an alga) may have been present in the common ancestor of Kinetoplastida and Euglenoida.  It was retained as an organelle in many euglenoids, but lost in kinetoplastids, while still leaving some traces in the present-day organisms.  A scenario in which the phototrophic endosymbiont contributed to the development of the glycosome from an ancestral peroxisome could be imagined.  Moreover, the finding that trypanosomes share metabolic features with plants may offer prospects for drug development.