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The production of fatty acids is an important cellular pathway for both cellular function and the development of engineered pathways for the synthesis of advanced biofuels. Despite the conserved reaction chemistry of various fatty acid synthase systems, the individual isozymes that catalyze these steps are quite diverse in their structural and biochemical features and are important for controlling differences at the cellular level. One of the key steps in the fatty acid elongation cycle is the enoyl-ACP (CoA) reductase function that drives the equilibrium forward toward chain extension. In this work, we report the structural and biochemical characterization of the trans-enoyl-CoA reductase from Treponema denticola (tdTer), which has been utilized for the engineering of synthetic biofuel pathways with an order of magnitude increase in product titers compared to those of pathways constructed with other enoyl-CoA reductase components. The crystal structure of tdTer was determined to 2.00 Å resolution and shows that the Ter enzymes are distinct from members of the FabI, FabK, and FabL families but are highly similar to members of the FabV family. Further biochemical studies show that tdTer uses an ordered bi-bi mechanism initiated by binding of the NADH redox cofactor, which is consistent with the behavior of other enoyl-ACP (CoA) reductases. Mutagenesis of the substrate binding loop, characterization of enzyme activity with respect to crotonyl-CoA, hexenoyl-CoA, and dodecenoyl-CoA substrates, and product inhibition by lauroyl-CoA suggest that this region is important for controlling chain length specificity, with the major portal playing a more important role for longer chain length substrates.

反式烯脂酰-CoA还原酶(trans-2, 3-enoyl-CoA reductase, ECR)是催化超长链脂肪酸(VLCFAs)合成的脂肪酰-CoA延长酶之一。根据已报道拟南芥等的ECR基因设计引物，采用RACE (rapid amplification of cDNA ends)方法从甘蓝型油菜中克隆ECR的全长cDNA序列和对应的基因组序列，命名为 BnECR (GenBank登录号分别为FJ899705和FJ899706)。序列分析结果显示， BnECR 的全长cDNA序列为1 328 bp，对应的基因组序列为2 093 bp，由4个外显子组成，在ORF的上、下游分别有一个163 bp的5′UTR和一个232 bp的3′UTR。根据编码区预测BnECR前体蛋白为一个310个氨基酸残基的多肽链，包含ECR蛋白的重要功能位点K 144 、R 145 及一个NAD(P)H结合基序G 225 SGGYQIPR/HG 234 。NCBI Blastn、氨基酸序列多重比对及保守域分析表明, 该基因与拟南芥 AtECR 基因的同源性最高，是对应拟南芥 AtECR 的垂直同源基因。RT-PCR分析表明， BnECR 基因在甘蓝型油菜根、茎、叶、花及角果中均有表达，其中在茎中的表达量最高。 BnECR 在高芥酸材料种子发育中后期的表达量显著高于低芥酸种子，表明 BnECR 可能参与甘蓝型油菜芥酸的合成。将 BnECR 克隆到酿酒酵母的穿梭表达载体中，分别转化野生型酵母By4743和突变体菌株YDL015c，添加半乳糖诱导表达。气相色谱分析表明， BnECR 在酿酒酵母中有效表达，转化菌株中的芥酸(C22:1)占总脂肪酸含量的1.34%，比对照增加了52%；对突变体的转化结果表明芥酸含量恢复到野生型水平。

Two fractions containing NADPH-enoyl CoA reductase activities were isolated from crude extracts of Candida albicans. One fraction (Type-I) having larger molecular weight utilizes 5-hydroxyundec-cis-2-enoyl CoA, oct-cis-2-enoyl CoA and oct-trans-2-enoyl CoA as substrates with Km values of 2.5×10-6M, 1.1×10-6M and 5.0×10-7M, respectively, while another fraction (Type-II) having smaller molecular weight utilizes these substrates with Km values of 3.0×10-6M, 5.3×10-5M and 1.0×10-5M, respectively. This indicates that there exist comparable differences between these two in their affinities especially for the latter two substrates. Some characterizations, such as, effects of pH and of heat treatment on the activities of these reductase preparations were also investigated.

Feeding of clofibrate to male rats leads to a 4–7 fold increase in the activity of the 4-enoyl-CoA reductase in the liver. Concomitantly the inhibition of fatty acid oxidation by pent-4-enoate is abolished, and an increased glucose formation in the presence of pent-4-enoate is observed. It is suggested that pent-4-enoate is converted to propionyl-CoA via the reaction sequence pent-4-enoyl-CoA→pent-2,4-dienoyl-CoA→pent-2-enoyl-CoA→propionyl-CoA + acetyl-CoA.

Background n-Butanol can serve as an excellent gasoline substitute. Naturally, it is produced by some Clostridia species which, however, exhibit only limited suitability for industrial n-butanol production. The yeast Saccharomyces cerevisiae would be an ideal host due to its high robustness in fermentation processes. Nevertheless, n-butanol yields and titers obtained so far with genetically engineered yeast strains are only low.