Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, P.O. Box 1600, Canberra A.C.T. Australia.
Plant Physiol. 1986 Jun;81(2):448-53. doi: 10.1104/pp.81.2.448.
The effect of temperature on accumulation of starch was studied in grain slices of wheat (Triticum aestivum cv SUN9E), taken 15 days after anthesis. As compared with pretreatment of such slices at 25 degrees C, pretreatment at 30 or 35 degrees C reduced the subsequent conversion of sucrose to starch. In contrast to rice (Oryza sativa cv Calrose), pretreatment of wheat soluble starch synthase in vitro at 30 degrees C or higher temperatures reduced its activity. In zymograms using nondenaturing polyacrylamide gel electrophoresis followed by activity staining, the slowest migrating band represented the most temperature sensitive isozyme. Although preincubation of a soluble enzyme sample in vitro at 25 degrees C did not result in loss of starch synthase activity, it did result in a gradual shift of zymogram banding pattern toward faster migrating species. Pretreatment of isolated starch granules at 40 degrees C increased their bound starch synthase activity. Both soluble and bound enzymes in the grains of whole wheat plants lost activity when the plants were held above 30 degrees C for 30 minutes or longer. Both activities lost from the grains after a 1 hour treatment at 37 degrees C were restored in 1 to 2 days by a return to 21 degrees C. In slices, inactivation of the soluble starch synthase was increased by incubation with 2,4-dinitrophenol. It is tentatively suggested that in vivo heat inactivation of soluble starch synthase may be a direct effect of heat on the enzyme protein and that of bound enzyme an indirect effect involving metabolic factors.
研究了在小麦（Triticum aestivum cv SUN9E）开花后 15 天的麦粒切片中，温度对淀粉积累的影响。与在 25°C 预处理相比，在 30°C 或 35°C 预处理会降低蔗糖向淀粉的后续转化。与水稻（Oryza sativa cv Calrose）不同，在 30°C 或更高温度下体外预处理小麦可溶性淀粉合酶会降低其活性。在使用非变性聚丙烯酰胺凝胶电泳进行同工酶电泳后，用活性染色的同工酶谱中，迁移最慢的条带代表最敏感的同工酶。尽管在 25°C 下体外预孵育可溶性酶样品不会导致淀粉合酶活性丧失，但它确实导致同工酶谱带模式逐渐向更快迁移的物种转移。在 40°C 下预处理分离的淀粉粒会增加其结合的淀粉合酶活性。当整个小麦植株的温度高于 30°C 并持续 30 分钟或更长时间时，植株内的可溶性和结合酶都会失去活性。在 37°C 下处理 1 小时后，从谷物中失去的两种活性在返回 21°C 后 1 至 2 天内均可恢复。在切片中，用 2,4-二硝基苯酚孵育会增加可溶性淀粉合酶的失活。我们推测，体内可溶性淀粉合酶的热失活可能是热对酶蛋白的直接影响，而结合酶的失活可能是涉及代谢因素的间接影响。
