Phosphoglucose isomerase from bananas: Partial characterization and relation to main changes in carbohydrate composition during ripening
Cordenunsi, B.R. (University of Sao Paulo (Brazil)) | do Nascimento, J.R.O. | da Mota, R.V. | Lajolo, F.M.
Some characteristics of phosphoglucose isomerase (PGI, EC 5. 3. 1. 9) from banana were measured during fruit ripening of three banana cultivars. In banana, PGI was present as two dimeric isoenzymes, named PGI sub1 and PGI sub2, which had similar native molecular masses but differed in relation to heat stability and isoelectric point. Total PGI activity showed a distinct two-step change during fruit ripening. Before the climacteric period, PGI activity gradually decreased with the starch content, then its activity began to increase with sucrose accumulation. The ratio of PGI sub1 and PGI sub2 was constant, indicating that both enzymes would be involved in starch degradation and sucrose synthesis. PGI activity and changes in carbohydrate composition suggests the existence of some control to fit the requirements of the intense carbon flow from starch to sucrose.
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