Fru 2,6-P2 and citrate: intracellular distribution in citrus tissues and effect on grapefruit leaf PFP.
Grapefruit leaf PFP was studied for its activation by fructose 2,6-bisphosphate (Fru 2,6-P2) in the forward and reverse reactions. In the glycolytic reaction, a Ka of 4.0 +/- 0.12 nM was obtained. This constant is affected by the presence of increasing concentrations of citrate (1, 5 and 20 nM) with a Ka(citrate) of 4.5 +/- 0.09, 6.9 +/- 0.05 and 38.2 +/- 1.4 respectively. The inhibition mode of citrate is competitive with Fru 2,6-P2, but non-linear in relation of increasing concentrations of the inhibitor. The intracellular distribution and concentration of the key regulatory metabolite Fru 2,6-P2 was further investigated in citrus leaves and juice cells. Fru 2,6-P2 was only found in the cytosol of juice cells. Fru 2,6-P2 was detected under both conditions with higher concentrations found under aerobiosis.
Van Praag
E
E
Kennedy-Leigh Centre for Horticultural Research, Hebrew University of Jerusalem, Rehovot, Israel.
Gonzalez
P
P
Brune
A
A
Goren
R
R
Zehavi
U
U
Echeverria
E
E
D019343:Citric Acid / Q000378:metabolism*; D002957:Citrus / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D005635:Fructosediphosphates / Q000378:metabolism*; D007424:Intracellular Fluid / Q000378:metabolism*; D007700:Kinetics; D010732:Phosphofructokinase-1 / Q000187:drug effects / Q000378:metabolism*; D018515:Plant Leaves / Q000201:enzymology / Q000378:metabolism*; D014018:Tissue Distribution
D005635:Fructosediphosphates; D019343:Citric Acid; C027652:fructose 2,6-diphosphate; D010732:Phosphofructokinase-1