Identification of the soluble starch synthase activities of maize endosperm
Identification of the soluble starch synthase activities of maize endosperm
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DOI：
10.1104/pp.120.1.205
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发表时间：
1999-05-01
期刊：
影响因子：
7.4
通讯作者：
Myers, AM
中科院分区：
文献类型：
--
作者：
Cao, HP;Imparl-Radosevich, J;Myers, AM
本研究鉴定了发育中的玉米胚乳中存在的可溶性淀粉水解酶（SS）的补体。du 1基因的产物DU 1是两种主要的可溶性SS之一。DU 1的C-末端450个残基包含8个在28种已知或预测的葡聚糖糖苷酶中保守的序列块。DU 1的这一区域在大肠杆菌中表达，并显示具有SS活性。DU 1特异性抗血清检测到一个可溶性胚乳蛋白超过200 kD，是缺乏DU 1突变体。这些抗血清消除了20%至30%的可溶性SS活性从内核提取物。抗血清对同工酶zSSI消除约60%的总可溶性SS，和免疫消耗的DU 1突变体提取物与此抗血清几乎消除SS活性。两个可溶性SS的活动，确定了电泳分离，其中每一个具体相关的SSI或DU 1。因此，DU 1和zSSI占绝大多数的可溶性SS活性存在于发育中的胚乳。在淀粉合成期间，两种同工酶的相对活性变化不明显。DU 1和zSSI可能是相互依赖的，因为缺乏DU 1的突变体提取物表现出显着的刺激剩余的SS活性。
This study identified the complement of soluble starch synthases (SSs) present in developing maize (Zea mays) endosperm. The product of the du1 gene, DU1, was shown to be one of the two major soluble SSs, The C-terminal 450 residues of DU1 comprise eight sequence blocks conserved in 28 known or predicted glucan synthases. This region of DU1 was expressed in Escherichia coli and shown to possess SS activity. DU1-specific antisera detected a soluble endosperm protein of more than 200 kD that was lacking in du1- mutants. These antisera eliminated 20% to 30% of the soluble SS activity from kernel extracts. Antiserum against the isozyme zSSI eliminated approximately 60% of the total soluble SS, and immunodepletion of du1- mutant extracts with this antiserum nearly eliminated SS activity. Two soluble SS activities were identified by electrophoretic fractionation, each of which correlated specifically with SSI or DU1. Thus, DU1 and zSSI accounted for the great majority of soluble SS activity present in developing endosperm. The relative activity of the two isozymes did not change significantly during the starch biosynthetic period. DU1 and zSSI may be interdependent, because mutant extracts lacking DU1 exhibited a significant stimulation of the remaining SS activity.