Characterization of a structurally and functionally diverged acyl-acyl carrier protein desaturase from milkweed seed
Characterization of a structurally and functionally diverged acyl-acyl carrier protein desaturase from milkweed seed
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DOI：
10.1023/a:1005821007291
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发表时间：
1997-04-01
影响因子：
5.1
通讯作者：
Shanklin, J
中科院分区：
文献类型：
--
作者：
Cahoon, EB;Coughlan, SJ;Shanklin, J
从乳草（Asclepias syriaca）种子中分离出结构变异的酰基-酰基载体蛋白（ACP）去饱和酶的cDNA，所述乳草种子是富含棕榈油酸（16：1 Delta（9））* 和顺式异油酸（18：1 Delta（11））的组织。表达马利筋cDNA的大肠杆菌提取物催化酰基-ACP底物的Delta（9）去饱和，并且重组酶对棕榈酰（16：0）-ACP的特异性比已知的Delta（9）-硬脂酰（18：0）-ACP去饱和酶高7至10倍，对肉豆蔻酰（14：0）-ACP的特异性高30倍。与迄今报道的其他变体酰基-ACP去饱和酶一样，与先前表征的Delta（9）-18：0-ACP去饱和酶相比，乳草酶在其N-末端附近含有较少的氨基酸。基于Δ（9）-18：0-ACP去饱和酶的N-末端缺失突变体的活性，该结构特征可能不能解释底物特异性的差异。
A cDNA for a structurally variant acyl-acyl carrier protein (ACP) desaturase was isolated from milkweed (Asclepias syriaca) seed, a tissue enriched in palmitoleic (16:1 Delta(9))* and cis-vaccenic (18:1 Delta(11)) acids. Extracts of Escherichia coli that express the milkweed cDNA catalyzed Delta(9) desaturation of acyl-ACP substrates, and the recombinant enzyme exhibited seven- to ten-fold greater specificity for palmitoyl (16:0)-ACP and 30-fold greater specificity for myristoyl (14:0)-ACP than did known Delta(9)-stearoyl (18:0)-ACP desaturases. Like other variant acyl-ACP desaturases reported to date, the milkweed enzyme contains fewer amino acids near its N-terminus compared to previously characterized Delta(9)-18:0-ACP desaturases. Based on the activity of an N-terminal deletion mutant of a Delta(9)-18:0-ACP desaturase, this structural feature likely does not account for differences in substrate specificities.