Studies on ATP:phosphofructokinase in ripening mango (Mangifera indica L.) fruit.
Rajiv Kumar, Selvaraj Y.
Author Affiliation: Fruit Biochemistry Laboratory, Indian Institute of Horticulture Research, Bangalore 560?089, India.
Current Science 58 : 666-668
Abstract : Mango fruits of cultivars Banganapalli, Dashehari, Fazli, Langra and Suvarnarekha, at the harvest maturity stage, were obtained from trees grown at the experimental orchard, Hessaraghatta. Fruits were ripened at ambient temperature (25±2°C) and at 70±5% RH. ATP:phosphofructokinase (PFK) activity was studied at four ripening stages: harvest maturity, half-ripe, ³/4-ripe and eating-ripe. PFK activity, expressed as µmol fructose-6-phosphate phosphorylated min-1 (mg protein)-1, was demonstrated only in the ³/4 ripe stage of cultivars Banganapalli, Dashehari and Langra, and at the eating-ripe stage of all five cultivars. The greatest activity (0.095±0.018) was recorded at the eating-ripe stage of cv. Langra. The partially purified enzyme preparation showed allosteric kinetics; an increasing substrate concentration gave a sigmoidal curve for enzyme activity. ATP at a high concentration acted as a negative allosteric modulator. The enzyme was activated by Pi, and inhibited by citrate and 5?-AMP. It is suggested that PFK plays a crucial role in the regulation of glycolysis in ripening mango fruits.