From owner-metabolic-reg@net.bio.net Mon Feb 10 22:00:00 1997
Path: biosci!IR2CBM.CNRS-MRS.FR!athel
From: athel@IR2CBM.CNRS-MRS.FR (Athel)
Newsgroups: bionet.metabolic-reg
Subject: Inorganic phosphate in plants
Date: 11 Feb 1997 00:59:38 -0800
Organization: CNRS
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In reply to a question from Guy Brown, David Fell wrote:

"The organism responds by induction of another enzyme that takes over
the role. e.g. there is no doubt that the glycolytic pathway is used in 
potatoes, but deleting pyruvate kinase gives virtually no observable
phenotype. It seems that a PEP phophatase takes over the role, and the
loss of ATP production is not significant. This is presumably a specific
adaptation in plants, because loss of pyruvate kinase is not generally
so benign."

My question is stimulated by David's comment, though it may not be
directly relevant to it. Does anyone know to what extent it is true (as
I was told a long time ago) that in plants inorganic phosphate fulfils
the role associated with ATP in animals, i.e. that phosphorylation of
many molecules is coupled to conversion of PPi to Pi rather than
conversion of ATP to ADP? If this is true,

1. Are there parallel (alternative) ATP-using and PPi-using enzymes?

2. Or are many of the usual ATP-dependent enzymes missing from plants?

3. If alternative enzymes exist, how do they affect energy regulation,
and do they permit the sort of response to loss of ATP production that
David refers to above?

4. References to reviews?

Athel

Home page: http://ir2lcb.cnrs-mrs.fr/lcbpage/athel/home_page.html
MCA FAQ: http://ir2lcb.cnrs-mrs.fr/lcbpage/athel/mcafaq.html
MCA chapter from my book:
http://ir2lcb.cnrs-mrs.fr/lcbpage/athel/fek10/mcai.html


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