ESCHERICHIA-COLI BETA-HYDROXYDECANOYL THIOESTER DEHYDRASE REACTS WITH NATIVE C-10 ACYL ACYL-CARRIER PROTEINS OF PLANT AND BACTERIAL ORIGIN
ESCHERICHIA-COLI BETA-HYDROXYDECANOYL THIOESTER DEHYDRASE REACTS WITH NATIVE C-10 ACYL ACYL-CARRIER PROTEINS OF PLANT AND BACTERIAL ORIGIN
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DOI：
10.1016/0003-9861(90)90339-z
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发表时间：
1990-08-01
影响因子：
3.9
通讯作者：
BROWSE, JA
中科院分区：
文献类型：
--
作者：
GUERRA, DJ;BROWSE, JA
β-羟基癸酰基-[酰基-载体-蛋白]脱氢酶催化大肠杆菌中不饱和脂肪酸形成的关键步骤。该反应的特征在于与天然C10酰基-酰基-载体蛋白（ACP）的结构在水相系统和底物固定化测定系统。该酶与E.大肠杆菌ACP、源自菠菜的重组ACP-I或蛋白A：ACP-I融合物（酰基硫酯）。底物之间的平衡产物分布存在差异。E.大肠杆菌酰基-ACP和重组酰基-ACP-I作为与β- OH 10：0、反式-2 10：1或顺式-3 10：1产生约等量（37摩尔%）的两种单烯，而与初始底物无关。相比之下，融合酰基-ACP-I仅产生17摩尔%的顺式-3 10：1与49摩尔%的反式-2 10：1存在于平衡。天然顺式-3 10：1的这些平衡值高于先前报道的使用N-乙酰基半胱胺硫酯作为底物的酶。每个β的Km值- OH 10：0 ACP底物彼此相似并且在体内浓度范围内（5-10 μ M）。脱水酶反应性更多地取决于酰基链长度而不是ACP结构或来源，因此不同于根据ACP结构区分的其它利用分支点ACP的酶（植物和细菌）（D. J. Guerra，J. B. Ohlrogge和M. Frentzen，1986，Plant Physl. 82，448-453）。
.beta.-Hydroxydecanoyl-[acyl-carrier-protein] dehydrase catalyzes the essential step in the formation of unsaturated fatty acids in Escherichia coli. This reaction was characterized with native C10 acyl-acyl-carrier protein (ACP) structures in both an aqueous phase system and a substrate immobilization assay system. The dehydrase is equally active with E. coli ACP, recombinant ACP-I derived from spinach, or protein A:ACP-I fusion (acyl-thioesters). There were differences among the substrates in terms of the equilibrium product distribution. Both E. coli acyl-ACP and recombinant acyl-ACP-I as cosubstrates with .beta.-OH 10:0, trans-2 10:1, or cis-3 10:1 yielded about equal amounts (37 mol%) of the two monoenes regardless of the initial substrate. In contrast, the fusion acyl-ACP-I yielded only 17 mol% cis-3 10:1 with 49 mol% trans-2 10:1 present at equilibrium. These equilibrium values for native cis-3 10:1 are higher than those reported previously for the dehydrase using N-acetylcysteamine thioesters as substrates. The Km values for each .beta.-OH 10:0 ACP substrate were similar to each other and within the range of in vivo concentrations (5-10 .mu.M). Dehydrase reactivity depends more on acyl chain length than ACP structure or origin and is therefore different from other branch point ACP-utilizing enzymes (plant and bacterial) which discriminate according to ACP structure (D. J. Guerra, J. B. Ohlrogge, and M. Frentzen, 1986, Plant Physl. 82, 448-453).