期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1991
卷号：88
期号：13
页码：5769-5773
DOI：10.1073/pnas.88.13.5769
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Starch biosynthesis has been studied by using amyloplasts isolated from cultured cells of sycamore trees (Acer pseudoplatanus L.). Highly purified intact amyloplasts, free from mitochondria and starch granules derived from broken amyloplasts, were isolated from a Percoll step gradient. Subsequently, the double silicone oil layer centrifugation technique was used to study adenylate transport in the amyloplasts. An adenylate-specific carrier was found to be active in the uptake of ATP, ADP, AMP, and most importantly, ADPglucose (ADP-Glc). Kinetic analyses showed that the uptake of these adenylates was mutually competitive with each other. In contrast to the mitochondrial adenylate carrier, in amyloplasts only ATP and ADP-Glc uptake were inhibited by carboxyatractyloside. Evidence is presented that the ADP-Glc transported into the amyloplast stroma can be used in starch synthesis catalyzed by starch synthase (ADP-Glc:1,4-alpha-D-glucan 4-alpha-D-glucosyltransferase, EC 2.4.1.21 ). We propose that starch biosynthesis in amyloplasts is tightly coupled with the direct transport of ADP-Glc synthesized in the cytosol by sucrose synthase (ADP-Glc:D-fructose 2-alpha-D-glucosyltransferase, EC 2.4.1.13 )
