淀粉分支酶3存在于水稻胚乳的淀粉粒之中

对水稻胚乳淀粉颗粒结合的淀粉分支酶进行了研究.酶活性分析表明水稻胚乳中存在着与淀粉颗粒结合的淀粉分支酶.氨基酸测序分析结果表明结合于水稻胚乳淀粉粒的淀粉分支酶是分子量为84 kD的淀粉分支酶3(rice starch branching enzyme 3; RBE3).从开花后5 d到种子成熟,淀粉颗粒结合的RBE3蛋白都保持较为稳定的含量.Northern 分析表明水稻胚乳发育过程中RBE4最先表达而RBE3和RBE1的表达滞后.综合以上研究结果说明RBE3存在于水稻胚乳的淀粉之中是由于RBE3与淀粉葡聚糖链具有较高亲和性而难以和葡聚糖链解离,进而随着淀粉粒的增长而被其包裹.

Starch Branching Enzyme 3 Occurs Within Starch Granules in Rice Endosperms

The starch branching enzyme bound to starch granule in rice endosperm was investigated in the present paper. The starch branching enzyme activity assay indicated that some branching enzymes were bound to the starch granule of endosperm in rice. The result of N-terminal protein sequencing suggests that RBE3 (rice starch branching enzyme 3, RBE3), an 84 kD protein, bound to the starch granule of endosperm in rice. The level of starch granule-bound RBE3 protein remained approximately constant during the rice seed development. Northern blot analysis revealed that RBE4 was the earliest expressed starch branching enzyme during the development of rice endosperm and, subsequently RBE3 and RBE1 were expressed. These results suggest that RBE3 is bound to starch granule due to its high affinity to starch in rice endosperms.