Sweetlove L J, Burrell M M, ap Rees T
Department of Plant Sciences, University of Cambridge, U.K.
Biochem J. 1996 Dec 1;320 ( Pt 2)(Pt 2):493-8. doi: 10.1042/bj3200493.
The aim of this work was to use tubers from transgenic lines of potato (Solanum tuberosum) containing increased amounts of ADPglucose pyrophosphorylase to study the role of this enzyme in the control of starch synthesis. A 4-5-fold increase in activity of the enzyme, achieved by transformation with the Escherichia coli ADPglucose pyrophosphorylase gene glgC-16, had no detectable effect on the starch content of developing or mature tubers. No significant effects were found on the contents of ADPglucose, UDPglucose, glucose 1-phosphate, glucose 6-phosphate, PP1, ATP and ADP. Flux from [U-14C]sucrose, supplied to tubers still attached to the plant, to starch increased roughly in proportion to the increase in ADPglucose pyrophosphorylase activity. These measurements of flux gave a response coefficient close to 1 for the activity of the pyrophosphorylase in respect of starch synthesis. Pulse-chase experiments with [U-14C]sucrose showed that the increased flux into starch in the transformed tubers was accompanied by an increased rate of starch turnover. Further experiments suggested that the increased turnover was associated with an increase in the capacity of the tubers to degrade starch.
这项工作的目的是利用含有增加量的ADP葡萄糖焦磷酸化酶的转基因马铃薯（Solanum tuberosum）品系的块茎，来研究这种酶在淀粉合成调控中的作用。通过用大肠杆菌ADP葡萄糖焦磷酸化酶基因glgC - 16进行转化，使该酶的活性提高了4 - 5倍，但对发育中的或成熟块茎的淀粉含量没有可检测到的影响。在ADP葡萄糖、UDP葡萄糖、葡萄糖1 - 磷酸、葡萄糖6 - 磷酸、PP1、ATP和ADP的含量上未发现显著影响。供应给仍附着在植株上的块茎的[U - 14C]蔗糖向淀粉的通量大致与ADP葡萄糖焦磷酸化酶活性的增加成比例增加。这些通量测量得出焦磷酸化酶活性相对于淀粉合成的响应系数接近1。用[U - 14C]蔗糖进行的脉冲追踪实验表明，转化块茎中进入淀粉的通量增加伴随着淀粉周转速率的提高。进一步的实验表明，周转增加与块茎降解淀粉的能力增强有关。
