Effect of ethylene treatment on the concentration of fructose-2,6-bisphosphate and on the activity of phosphofructokinase 2/fructose-2,6-bisphosphatase in banana.
Preclimacteric bananas fruits were treated for 12 h with ethylene to induce the climacteric rise in respiration. One day after the end of the hormonal treatment, the two activities of the bifunctional enzyme, phosphofructokinase 2/fructose-2,6-bisphosphatase started to increase to reach fourfold their initial value 6 days later. By contrast, the activities of the pyrophosphate-dependent and of the ATP-dependent 6-phosphofructo-1-kinases remained constant during the whole experimental period, the first one being fourfold greater than the second. The concentrations of fructose 2,6-bisphosphate and of fructose 1,6-bisphosphate increased in parallel during 4 days and then slowly decreased, the second one being always about 100-fold greater than the first. The change in fructose 2,6-bisphosphate concentration can be partly explained by the rise of the bifunctional enzyme, but also by an early increase in the concentration of fructose 6-phosphate, the substrate of all phosphofructokinases, and also by the decrease in the concentration of glycerate 3-phosphate, a potent inhibitor of phosphofructokinase 2. The burst in fructose 2,6-bisphosphate and the activity of the pyrophosphate-dependent phosphofructokinase, which is in banana the only enzyme known to be sensitive to fructose 2,6-bisphosphate, can explain the well-known increase in fructose 1,6-bisphosphate which occurs during ripening.
Mertens
E
E
Laboratoire de Chimie Physiologique, Université Catholique de Louvain, Bruxelles, Belgium.
Marcellin
P
P
Van Schaftingen
E
E
Hers
H G
HG
D005030:Ethylenes / Q000494:pharmacology*; D005635:Fructosediphosphates / Q000378:metabolism*; D005638:Fruit; D006598:Hexosediphosphates / Q000378:metabolism*; D007700:Kinetics; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D013997:Time Factors
D005030:Ethylenes; D005635:Fructosediphosphates; D006598:Hexosediphosphates; C027652:fructose 2,6-diphosphate; C036216:ethylene; D017853:Phosphotransferases (Alcohol Group Acceptor); D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases; C029063:fructose-1,6-diphosphate