Curá J A, Tolmasky D S, Lepek V C, Lerner L R, Salerno J C, Krisman C R
Instituto de Investigaciones Bioquímicas Luis F. Leloir Fundación Campomar, Argentina.
Cell Mol Biol (Noisy-le-grand). 1994 Nov;40(7):1007-20.
Starch biogenesis in corn endosperm from Flint, Sugary, Waxy, as a function of the grain filling/period was studied. We have differentially identified the initiation from the elongation process. After incubating under unprimed conditions, two glucose radiolabelled protein bands of 39,5 and 36 kDa were obtained. UDP(14C)Glc was the preferred glucosyl donor but also ADP(14C)Glc was. It was additionally found that more than one glucose was transferred to the protein or to the alpha 1,4-glucan linked to protein from UDPGlc. These results were supported by the fact that the glucosylated protein from UDPGlc liberates maltooligosaccharides after alpha- or beta-amylase treatment. The elongation activity in the first steps related to the glucan linked to protein is different from starch synthase. Therefore, we are proposing a model for starch biogenesis where two new transglucosylating enzyme activities are necessary to prepare the primer for starch synthase.
研究了硬粒型、粉质型、糯质型玉米胚乳中淀粉生物合成与籽粒灌浆期的关系。我们已区分了起始过程和延伸过程。在未引发条件下孵育后，获得了两条葡萄糖放射性标记的蛋白带，分子量分别为39.5 kDa和36 kDa。UDP(14C)Glc是首选的葡萄糖基供体，但ADP(14C)Glc也是。此外还发现，不止一个葡萄糖从UDPGlc转移到蛋白质或与蛋白质相连的α-1,4-葡聚糖上。UDPGlc糖基化蛋白经α-淀粉酶或β-淀粉酶处理后释放出麦芽寡糖，这一事实支持了上述结果。与蛋白质相连的葡聚糖第一步的延伸活性不同于淀粉合酶。因此，我们提出了一个淀粉生物合成模型，其中需要两种新的转糖基酶活性来为淀粉合酶制备引物。
