pre-mitochondrial electron transport

James O. McInerney Ph.D. jamm at nhm.ac.uk
Mon Apr 15 04:43:32 EST 1996


Many thanks to Ron for the entertaining reply. I'm afraid
though that Andrew's answer is closer to what I was looking
for.  But it was definitely entertaining.

Andrew wrote...

> metabolism of Giardia) use glycolysis. The end-product of this
> is pyruvate. Instead of the usual conversion of pyruvate to
> acetyl-CoA by the pyruvate dehydrogenase complex which occurs
> in the mitochondrion-containing eukaryotes, organisms like
> Giardia use pyruvate:ferredoxin oxidoreductase.

There are a great many inconsistencies between trees derived
from sequences from organisms close to the base of the tree of life
(check out the 9404 archive of this newsgroup for an excellent
debate on this).  This has led to numerous chimeric/endosymbiont/
lateral transfer hypotheses (each with their own merits).  Now 
glycolysis is not clearly proven to be strictly vertically transmitted 
through eukaryotes (correct me if I'm wrong but pyruvate:ferredoxin 
oxidoreductase in the amitochondrial T. vaginalis is closely related to 
the bacterial gene pyruvate:flavodoxin oxidoreductase)  so this gene may 
be endosymbiotic in origin (Hrdy and Muller, 1995. J. mol. Evol.).

Then there is the GAPDH question!!

So again I put out the question (maybe clearer this time).  Lets say 
glycolysis is bacterial in origin (devil's advocate maybeee?), the 
pyruvate dehydrogenase complex is mitochondrial and hydrogenosomes in 
Trichomonas are modified mitochondria.....what did these early 
amitochondrial eukaryotes do for energy?  OR did they exist at all?

Note 1: I still know nothing about biochemistry
Note 2: This is not my field of study, but it's damn interesting.

Dr. James O. McInerney Ph.D.        Phone/Voicemail: +44 171 938 9247
Senior Scientific Officer,          email:j.mcinerney at nhm.ac.uk
The Natural History Museum,         
Cromwell Road,
London SW7 5BD

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