>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,
I have heard at a few occasions that polyphosphates of sometimes
considerable length (40-50 maximum) can take over the role of ATP. I don't
remember any details other than that one of the lectures was by Kornberg.
>>1. Are there parallel (alternative) ATP-using and PPi-using enzymes?
A good example is the PPi dependent phosphofructokinase of Trichomonas
vaginalis. Almost always PFK is ATP dependent. See also Mertens, E.
Parasitology Today 9, 122-126.
>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?
PPi-PFK has a key role in the metabolism of T. vaginalis (Microbiology 142,
3337-3345. 1996).
>Athel
>
My two cents worth,
Benno ter Kuile
