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Sucrose phosphate synthase and other sucrose metabolizing enzymes in fruits of various species.

Hubbard, N. L., Pharr, D. M. and Huber, S. C.

Physiologia Plantarum Year: 1991 Vol: 82 Issue: 2 Pages: 191-196 Ref: 22 ref.

1991

บทคัดย่อ

Sucrose phosphate synthase and other sucrose metabolizing enzymes in fruits of various species.

Recent reports have suggested that sucrose phosphate synthase, a key enzyme in sucrose biosynthesis in photosynthetic source tissues, may also be important in some sucrose-accumulating sink tissues. Experiments were conducted to determine if sucrose phosphate synthase is involved in sucrose accumulation in fruits of several species. Peach (NCT 516) and strawberry (cv. Chandler) fruits were harvested directly from the plant at various stages of fruit development. Kiwifruit, pawpaw, pineapple and mango fruits were sampled in postharvest storage over a period of several days. Carbohydrate concentrations and activities of sucrose phosphate synthase, sucrose synthase, and acid and neutral invertases were measured. All fruits showed significant sucrose phosphate synthase activity. Moreover, in fruits from all species except pineapple and pawpaw, an increase in sucrose phosphate synthase activity occurred which was associated with the accumulation of sucrose in situ. The increase in sucrose concentration in peaches was also associated with an increase in sucrose synthase activity and, in strawberries, with increased activity of both sucrose synthase and neutral invertase. The hexose pools in all fruits consisted of equimolar concentrations of fructose and glucose, except in mango. In mango, the fructose to glucose ratio increased from 2 to 41 during ripening as sucrose concentration more than doubled. The results indicate that activities of the sucrose metabolizing enzymes, including sucrose phosphate synthase, within the fruit itself, are important in determining the soluble sugar content of fruits of many species. This appears to be true for fruits which sweeten from a starch reserve and in fruits from sorbitol translocating species, raffinose saccharide translocating species, and sucrose translocating species.