Foyer C, Rowell J, Walker D
Arch Biochem Biophys. 1983 Jan;220(1):232-8. doi: 10.1016/0003-9861(83)90405-8.
Protoplasts from the leaves of wheat, spinach, and barley were found to synthesize [14C]sucrose from 14CO2 at rates comparable with those of the parent tissue. CO2 fixation and sucrose biosynthesis ceased virtually immediately when the light was switched off. The effect of sucrose pretreatment on the rate of de novo sucrose biosynthesis was found to vary with leaf age and with plant species. Protoplasts from young wheat and spinach leaves showed an apparent stimulation of the rate of sucrose biosynthesis after sucrose pretreatment. In protoplasts from mature leaves of spinach, sucrose pretreatment produced inhibition. After sucrose pretreatment protoplasts from mature spinach leaves showed low rates of CO2 fixation, and sucrose biosynthesis compared with controls. Conversely, with protoplasts from mature leaves of wheat and barley, the rate of CO2 fixation was unchanged and there was little or no effect on the rate of sucrose biosynthesis after sucrose pretreatment. Preincubation with sucrose had no effect on the activity of sucrose-phosphate synthetase (EC 2.4.1.14), cytoplasmic fructose-1,6-bisphosphatase (EC 3.1.3.11), or UDPglucose pyrophosphorylase (EC 2.7.7.9) from spinach leaves. It was concluded that there is no direct feedback inhibition of sucrose on the sucrose biosynthetic pathway in leaves of spinach, wheat, and barley. The mechanism of inhibition of sucrose biosynthesis by sucrose in spinach remains to be elucidated.
研究发现，小麦、菠菜和大麦叶片的原生质体能够以与亲本组织相当的速率从(^{14}CO_2)合成([^{14}C])蔗糖。当光照关闭时，(CO_2)固定和蔗糖生物合成几乎立即停止。结果表明，蔗糖预处理对从头合成蔗糖速率的影响因叶片年龄和植物种类而异。蔗糖预处理后，来自小麦和菠菜幼叶的原生质体蔗糖生物合成速率明显加快。对于菠菜成熟叶片的原生质体，蔗糖预处理则产生抑制作用。与对照相比，蔗糖预处理后菠菜成熟叶片的原生质体(CO_2)固定率和蔗糖生物合成率较低。相反，对于小麦和大麦成熟叶片的原生质体，(CO_2)固定率不变，蔗糖预处理后对蔗糖生物合成速率几乎没有影响。蔗糖预孵育对菠菜叶片中蔗糖磷酸合成酶（EC 2.4.1.14）、细胞质果糖-1,6-二磷酸酶（EC 3.1.3.11）或UDP葡萄糖焦磷酸化酶（EC 2.7.7.9）的活性没有影响。由此得出结论，在菠菜、小麦和大麦叶片中，蔗糖对蔗糖生物合成途径不存在直接的反馈抑制作用。菠菜中蔗糖抑制蔗糖生物合成的机制仍有待阐明。
