Cell organelles

Fred Opperdoes opperd at licr.ucl.ac.be
Mon Jul 29 03:59:31 EST 1996


Hi there,
The article posted by Krystyna Kielan Rybicka on the bionet.parasitology
newsgroup on the existence of glycogen containing particles called
"glycosomes" in almost all animal is interesting but provokes a large
amount of confusion. As you probably all know glycosomes are the membrane
surrounded microbody-like organelles of trypanosomatid and bodonid
flagellated protists that belong to the order of the Kinetoplastida. This
organelle, is unique to the Kinetoplastida. Glycosomes contain the early
enzymes of the glycolytic pathway and glycerol metabolism, such as
hexokinase, phosphoglucose isomerase, phosphofructokinase, aldolase,
triosephosphate isomerase, glyceraldehyde-phosphate dehydrogenase,
phosphoglycerate kinase, glycerol kinase and glycerophosphate
dehydrogenase. They also contain enzymes involved in such diversed pathways
as carbon-dioxide 
fixation, pyrimidine biosynthesis, ether-lipid biosynthesis and purine
salvage. The organelles resemble the peroxisomes of other eukaryotic
organisms in that they may contain the enzymes catalase and superoxide
dismutase, Futhermore their enzymes are imported into the organelly with
the help of at least two different types of import signals, a C-terminal
tripeptide (SKL or similar) and a N-terminal signal peptide, that have also
been identified for peroxisomal enzymes. As such the glycosomes are
bonafide organelles tha have established their name in the parasitological,
biochemical, cell biological and molecular biological literature. A simple
search of the Medline (1966-now) database using the keyword "glycosom?"
reveals 116 articles of which only 5 do not deal with the glycosomes of the
trypanosomatidae. Indeed four of them refer to organelles of glycogen
metabolism, the first of which appeared in Russian in 1977, followed then
by a few others. Almost nothing was published on the subject in the last 15
years. The first paper on trypanosomatid glycosomes also appeared in 1977,
but in English in FEBS letters and this has led to numerous more
publications on this subject by many different laboratories from all over
the world. I suggest that we reserve the name glycosomes for the
trypanosomatid organelles and use a different name or description for the
glycogen-containing articles of animal cells.

Fred R. Opperdoes




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