Marshall J, Sidebottom C, Debet M, Martin C, Smith A M, Edwards A
John Innes Centre, Norwich, United Kingdom.
Plant Cell. 1996 Jul;8(7):1121-35. doi: 10.1105/tpc.8.7.1121.
The major isoform of starch synthase from the soluble fraction of developing potato tubers has been purified and used to prepare an antibody and isolate a cDNA. The protein is 140 kD, and it is distinctly different in predicted primary amino acid sequence from other isoforms of the enzyme thus far described. Immunoinhibition and immunoblotting experiments and analysis of tubers in which activity of the isoform was reduced through expression of antisense mRNA revealed that the isoform accounts for approximately 80% of the activity in the soluble fraction of the tuber and that it is also bound to starch granules. Severe reductions in activity had no discernible effect on starch content or amylose-to-amylopectin ratio of starch in tubers. However, they caused a profound change in the morphology of starch granules, indicative of important underlying changes in the structure of starch polymers within the granule.
已从发育中的马铃薯块茎可溶性部分纯化出淀粉合酶的主要同工型,并用于制备抗体和分离cDNA。该蛋白质为140 kD,其预测的一级氨基酸序列与迄今为止描述的该酶的其他同工型明显不同。免疫抑制和免疫印迹实验以及对通过反义mRNA表达降低同工型活性的块茎的分析表明,该同工型约占块茎可溶性部分活性的80%,并且它也与淀粉颗粒结合。活性的严重降低对块茎中淀粉含量或淀粉的直链淀粉与支链淀粉比例没有明显影响。然而,它们导致淀粉颗粒形态发生深刻变化,这表明颗粒内淀粉聚合物结构发生了重要的潜在变化。