Identification of a Long-Chain Fatty Acid Elongase from Nannochloropsis sp. Involved in the Biosynthesis of Fatty Acids by Heterologous Expression in Saccharomyces cerevisiae

The marine microalga Nannochloropsis sp.contains various elongases and desaturases that are critical for biosynthesis of polyunsaturated fatty acids.A full-length cDNA encoding a long-chain fatty acid elongase,named Ns FAE,was cloned from Nannochloropsis sp..The open reading frame of Ns FAE(GenBank accession no.MF680548)consisted of 1068 bp and encoded a predicted protein of 355 amino acids with molecular mass 38.8 k Da.The deduced polypeptide showed 43%–44%identity to fatty acyl elongases from other algae.RT-PCR experiments indicated that the Ns FAE gene exhibited the highest expression in Nannochloropsis sp.at 72 h(i.e.,during the third growth stage)and the expression was significantly lower in the other four growth stages.Plasmid p Ns FAE-CRISPR and a recombinant DNA fragment(ADH1p-Ns FAE-CYCt)were transformed into Saccharomyces cerevisiae strain BY4742 using the CRISPR-Cas system.Yeast transformants containing Ns FAE produced three fatty acids not normally present in wild-type BY4742-linoleic acid,linolenic acid and eicosadienoic acid-indicating that Ns FAE encodes a functional elongase enzyme.

Molecular evidence for blocking erucic acid synthesis in rapeseed(Brassica napus L.) by a two-base-pair deletion in FAE1(fatty acid elongase 1)

DNA sequences of fatty acid elongase 1 genes FAE1.1 （EA） and FAE1.2 （Ec） were isolated and characterized for 30 com- mercialized low erucic acid rapeseed （LEAR） cultivars in China. Four types of independent mutation leading to low erucic acid trait were found, i.e., a single-base transition （eAl）, a two-base deletion （ec2） and four-base deletion （eC4） as well as single-base transition with a four-base deletion （eA.）. Three genotypes, i.e., eA1eA1eC2eC2, eA1eA1eC4eC4 and eA.eA.ec4ec4 were responsible for LEA content in storage Iipids of different rapeseed cultivars. Most of the LEAR cultivars had a genotype of eA1eA1ec2ec2, which were descended from the first LEAR cultivar, Oro. Yeast expression analysis revealed that two-base-pair （AA） deletion （ec2） at the base sites of 1 422-1 423 in the C genome FAE1 gene resulted in the absence of the condensing enzyme and led to the failure to produce erucic acid. Coexpression of FAE1 and ketoacyI-CoA reductase （KCR） or enoyI-CoA reductase （ECR） was found in high erucic acid rapeseed （HEAR） but not in LEAR （eA1eA1ec2ec2oreA1eA1ec4ec4）. Moreover, KCR and ECR were still coordinately regulated in eA1eA1ec2ec2 or eA1eA1ec4ec4 genotypes, suggesting that the expression of two genes was tightly linked. In addition, specific detection methods were developed by high-resolution melting curve analysis in order to detect eA1 and ec4.

Submesoscale characteristics and transcription of a fatty acid elongase gene from a freshwater green microalgae, Myrmecia incisa Reisigl

Myrmecia incisa is a green coccoid freshwater microalgae, which is rich in arachidonic acid (ArA, C20: 4?-6, Δ5, 8, 11, 14), a long chain polyunsaturated fatty acid (PUFA), especially under nitrogen starvation stress. A cDNA library of M. incisa was constructed with λ phage vectors and a 545 nt expressed sequence tag (EST) was screened from this library as a putative elongase gene due to its 56% and 49% identity to Marchantia polymorpha L. and Ostreococcus tauri Courties et Chrétiennot-Dinet, respectively. Based upon this EST sequence, an elongase gene designated MiFAE was isolated from M. incisa via 5′/3′ rapid amplification of cDNA ends (RACE). The cDNA sequence was 1 331 bp long and included a 33 bp 5′-untranslated region (UTR) and a 431 bp 3′-UTR with a typical poly-A tail. The 867 bp ORF encoded a predicted protein of 288 amino acids. This protein was characterized by a conserved histidine-rich box and a MYxYY motif that was present in other members of the elongase family. The genomic DNA sequence of MiFAE was found to be interrupted by three introns with splicing sites of Introns I (81 bp), II (81 bp), and III (67 bp) that conformed to the GT-AG rule. Quantitative real-time PCR showed that the transcription level of MiFAE in this microalga under nitrogen starvation was higher than that under normal condition. Prior to the ArA content accumulation, the transcription of MiFAE was enhanced, suggesting that it was possibly responsible for the ArA accumulation in this microalga cultured under nitrogen starvation conditions.

Long-chain acyl-CoA synthetase in fatty acid metabolism involved in liver and other diseases:An update

Long-chain acyl-Co A synthetase(ACSL) family members include five different ACSL isoforms, each encoded by a separate gene and have multiple spliced variants. ACSLs on endoplasmic reticulum and mitochondrial outer membrance catalyze fatty acids with chain lengths from 12 to 20 carbon atoms to form acyl-Co As, which are lipid metabolic intermediates and involved in fatty acid metabolism, membrane modifications and various physiological processes. Gain- or lossof-function studies have shown that the expression of individual ACSL isoforms can alter the distribution and amount of intracellular fatty acids. Changes in the types and amounts of fatty acids, in turn, can alter the expression of intracellular ACSLs. ACSL family members affect not only the proliferation of normal cells, but the proliferation of malignant tumor cells. They also regulate cell apoptosis through different signaling pathways and molecular mechanisms. ACSL members have individual functions in fatty acid metabolism in different types of cells depending on substrate preferences, subcellular location and tissue specificity, thus contributing to liver diseases and metabolic diseases, such as fatty liver disease, obesity, atherosclerosis and diabetes. They are also linked to neurological disorders and other diseases. However, the mechanisms are unclear. This review addresses new findings in the classification and properties of ACSLs and the fatty acid metabolismassociated effects of ACSLs in diseases.

Impacts of the unsaturation degree of long-chain fatty acids on the volatile fatty acid profiles of rumen microbial fermentation in goats in vitro

This study investigated the impacts of the degree of unsaturation （unsaturity） of long-chain fatty acids on volatile fatty acid （VFA） profiles of rumen fermentation in vitro. Six types of long-chain fatty acids, including stearic acid （C18：0, control group）, oleic acid （C18：1, n-9）, linoleic acid （C18：2, n-6）, a-linolenic acid （C18：3, n-3）, arachidonic acid （C20：4, n-6） and eicosapentaenoic acid （C20：5, n-3）, were tested. Rumen fluid from three goats fitted with ruminal fistulae was used as inoculum and the inclusion rate of long-chain fatty acid was at 3% （w/w） of substrate. Samples were taken for VFA analysis at 0, 3, 6, 9, 12, 18 and 24 h of incubation, respectively. The analysis showed that there were significant differences in the total VFA among treatments, sampling time points, and treatment×time point interactions （P〈0.01）. a-Linolenic acid had the highest total VFA （P〈0.01） among different long-chain fatty acids tested. The molar proportion of acetate in total VFA significantly differed among treatments （P〈0.01） and sampling time points （P〈0.01）, but not treatment×time point interactions （P〉0.05）. In contrast, the molar proportion of propionate did not differ among treatments during the whole incubation （P〉0.05）. However, for butyrate molar proportions, significant differences were found not only among sampling time points but also among treatments and treatment×time point interactions （P〈0.01）, with eicosapentaenoic acid having the highest value （P〈0.01）. Additionally, no statistically significant differences were found in the acetate to propionate ratios among treatments groups （P〉0.05）, even the treatments stearic acid and a-linolenic acid were numerically higher than the others. The inclusion of 3% long-chain unsaturated fatty acids differing in the degree of unsaturation brought out a significant quadratic regression relation between the total VFA concentration and the double bond number of fatty acid. In conclusion, the a-linolenic acid with 3 double bonds appeared better for improving rumen microbial fermentation and the total VFA concentration.

The LXRB-SREBP1 network regulates lipogenic homeostasis by controlling the synthesis of polyunsaturated fatty acids in goat mammary epithelial cells

Background:In rodents,research has revealed a role of liver X receptors(LXR) in controlling lipid homeostasis and regulating the synthesis of polyunsaturated fatty acids(PUFA).Recent data suggest that LXRB is the predominant LXR subtype in ruminant mammary cells,but its role in lipid metabolism is unknown.It was hypothesized that LXRB plays a role in lipid homeostasis via altering the synthesis of PUFA in the ruminant mammary gland.We used overexpression and knockdown of LXRB in goat primary mammary epithelial cells(GMEC) to evaluate abundance of lipogenic enzymes,fatty acid profiles,content of lipid stores and activity of the stearoyl-Co A desaturase(SCD1) promoter.Results:Overexpression of LXRB markedly upregulated the protein abundance of LXRB while incubation with si RNA targeting LXRB markedly decreased abundance of LXRB protein.Overexpression of LXRB plus T0901317(T09,a ligand for LXR) dramatically upregulated SCD1 and elongation of very long chain fatty acid-like fatty acid elongases 5–7(ELOVL 5–7),which are related to PUFA synthesis.Compared with the control,cells overexpressing LXRB and stimulated with T09 had greater concentrations of C16:0,16:1,18:1n7,18:1n9 and C18:2 as well as desaturation and elongation indices of C16:0.Furthermore,LXRB-overexpressing cells incubated with T09 had greater levels of triacylglycerol and cholesterol.Knockdown of LXRB in cells incubated with T09 led to downregulation of genes encoding elongases and desaturases.Knockdown of LXRB attenuated the increase in triacylglycerol and cholesterol that was induced by T09.In cells treated with dimethylsulfoxide,knockdown of LXRB increased the concentration of C16:0 at the expense of C18:0,while a significant decrease in C18:2 was observed in cells incubated with both si LXRB and T09.The abundance of sterol regulatory element binding transcription factor 1 precursor(p SREBP1) and its mature fragment(n SREBP1) was upregulated by T09,but not LXRB overexpression.In the cells cultured with T09,knockdown of LXRB downregulated the abundance for p SREBP1 and n SREBP1.Luciferase reporter assays revealed that the activities of wild type SCD1 promoter or fragment with SREBP1 response element(SRE) mutation were decreased markedly when LXRB was knocked down.Activity of the SCD1 promoter that was induced by T09 was blocked when the SRE mutation was introduced.Conclusion:The current study provides evidence of a physiological link between the LXRB and SREBP1 in the ruminant mammary cell.An important role was revealed for the LXRB-SREBP1 network in the synthesis of PUFA via the regulation of genes encoding elongases and desaturases.Thus,targeting this network might elicit broad effects on lipid homeostasis in ruminant mammary gland.

Effects of long-chain fatty acid supplementation on the growth performance of grower and finisher pigs: a meta-analysis

Background: Supplementation of feed with long-chain fatty acids(LCFAs) during the grower and finisher phases has long been discussed as a growth promotion strategy in pigs, but its effects are inconsistent. The purpose of our study was to comprehensively evaluate its effects on the growth performance based on the average daily gain(ADG), average daily feed intake(ADFI) and gain: feed(G:F) ratio and to unveil the roles of the basal diet, LCFA concentration and LCFA saturation.Results: We searched the Pub Med and Web of Science databases(articles published from Jan 1 st, 2000, to Sep 30 th,2018;restricted to English) and compared LCFA-supplemented diets with control diets. We retrieved 2346 studies, 18 of which(1314 pigs, 26 records) were eligible for our analysis. We used a random-effects model to calculate the weighted mean differences(WMDs) and 95% confidence intervals(CIs). LCFA supplementation in the grower-finisher phase improved the ADG(WMD = 41.74 g/d, 95% CI: 8.81 to 74.66, P = 0.013) and G:F ratio(WMD = 0.019, 95% CI: 0.006 to 0.032, P = 0.003). For supplementation solely in the finisher phase, we found a similar performance in the ADG(WMD = 39.93 g/d, 95% CI: 26.48 to 53.38, P < 0.001) and G:F ratio(WMD = 0.019, 95% CI: 0.006 to 0.032, P < 0.001) but a reduction in the ADFI(WMD =-83.863 g/d, 95% CI:-156.157 to-11.569, P = 0.023). Specifically, approximately 5%LCFA supplementation in the finisher phase had significant effects on the ADG(WMD = 51.385 g/d, 95% CI: 35.816 to66.954, P < 0.001), ADFI(WMD =-102.869 g/d, 95% CI:-189.236 to-16.502, P = 0.02) and G:F ratio(WMD = 0.028, 95%CI: 0.018 to 0.039, P < 0.001), whereas a concentration of approximately 1% exhibited no effects.Conclusions: Overall, regardless of the basal diet and saturation, LCFA supplementation greatly improves the growth performance of grower and finisher pigs, primarily by increasing the energy density.

The effects of the unsaturated degree of long-chain fatty acids on the rumen microbial protein content and the activities of transaminases and dehydrogenase in vitro

This study investigated the effects of the degree of unsaturation（unsaturity） of long-chain fatty acids on microbial protein content and the activities of transaminases and dehydrogenase in vitro using goat rumen fluid as the cultural medium.Six types of fatty acids,stearic acid（C18：0,group A,control group）,oleic acid（C18：1,n-9,group B）,linoleic acid（C18：2,n-6,group C）,α-linolenic acid（C18：3,n-3,group D）,arachidonic acid（C20：4,n-6,group E）,and eicosapentaenoic acid（C20：5,n-3,group F）,were tested,and the inclusion ratio of each fatty acid was 3%（w/w） in total of culture substrate.Samples were taken at 0,3,6,9,12,18 and 24 h,respectively,during culture for analyses.Compared with stearic acid,linoleic acid,a-linolenic acid,and arachidonic acid increased the bacterial protein content,while oleic acid and eicosapentaenoic acid had no significant effects;the protozoal protein content was reduced for all the unsaturated fatty acids,and the magnitude of the reduction appeared to be associated with the degree of unsaturity of fatty acids.The total microbial protein content was dominantly accounted by the protozoal protein content（about 4-9 folds of the bacterial protein）,and only increased by linoleic acid,but reduced by oleic acid,arachidonic acid and eicosapentaenoic acid.There were no significant effects in the activities of both glutamic oxaloacetic transaminase（GOT） and glutamic-pyruvic transaminase（GPT） for all the other fatty acids,except for arachidonic acid which enhanced GOT activity and oleic acid which enhanced GPT activity.The total dehydrogenase activity was positively correlated with the degree of unsaturation of fatty acids.In conclusion,the inclusion of 3%of long-chain unsaturated fatty acids increased bacterial protein content,whereas reduced protozoal protein content and enhanced dehydrogenase activity.The fatty acids with more than three double bonds had detrimental effects on the microbial protein content.This work demonstrates for the first time the effect rule of the unsaturation degree of long-chain fatty acids on the rumen microbial protein in vitro.

Study on Extracting Rare Earth from Sulfate System by Long-Chain Fatty Acid

The extraction of rare earths by long-chain fatty acid in kerosene from sulphate system was described.It was demonstrated from the experimental results that the ratio of kerosene: fatty acid: isooctanol = 55 : 30: 15 ( V/V),By the saturation capability method and the slope method, the extracted reaction mechanism of the extraction of rare earth was studied.It is shown that the extraction reaction conform to the cation exchange reaction mechanism.The extracted sequence of rare earth was determined in this system and it is shown that there is no tetrad effect and the position of yttrium is between lanthanum and cerium.

Natural long-chain saturated fatty acids doped LNPs enabling spleen selective mRNA translation and potent cancer immunotherapy

Rationally tailored lipid nanoparticles(LNPs)with efficient and tunable delivery of mRNA in vivo are crucial for mRNA vaccines.Selective expression of antigenic protein in lymphoid tissues/organs could improve the immunostimulatory efficacy and safety of LNPs-based mRNA vaccines.Inspired by the metabolic behavior that long-chain saturated fatty acids tending to enter lymphoid tissue rather than the liver,we developed fatty acid-doped LNPs capable of mediating differential protein expressions in the liver and spleen when administered intravenously.When the molar ratio of saturated fatty acid located 60%–70%,the doped LNPs achieved the spleen selective mRNA translation.The mechanism could be attributed to the different cellular uptake behaviors of saturated fatty acids in hepatocytes.Immunization with a model antigen(ovalbumin)mRNA-loaded spleen selective LNPs,we observed enhanced antigen-specific T cell immune responses,and potent immunotherapeutic and immunoprophylactic efficacy in the mouse lymphoma model.Our natural long-chain saturated fatty acids metabolic characteristics-inspired design of LNPs for spleen-selective mRNA vaccines delivery will provide references for designing mRNA vaccines with high efficacy and safety for tumor immunotherapy.

Fatty acid metabolism and acyl-CoA synthetases in the liver-gut axis

Fatty acids are energy substrates and cell components which participate in regulating signal transduction,transcription factor activity and secretion of bioactive lipid mediators.The acyl-CoA synthetases(ACSs)family containing 26 family members exhibits tissue-specific distribution,distinct fatty acid substrate preferences and diverse biological functions.Increasing evidence indicates that dysregulation of fatty acid metabolism in the liver-gut axis,designated as the bidirectional relationship between the gut,microbiome and liver,is closely associated with a range of human diseases including metabolic disorders,inflammatory disease and carcinoma in the gastrointestinal tract and liver.In this review,we depict the role of ACSs in fatty acid metabolism,possible molecular mechanisms through which they exert functions,and their involvement in hepatocellular and colorectal carcinoma,with particular attention paid to long-chain fatty acids and small-chain fatty acids.Additionally,the liver-gut communication and the liver and gut intersection with the microbiome as well as diseases related to microbiota imbalance in the liver-gut axis are addressed.Moreover,the development of potentially therapeutic small molecules,proteins and compounds targeting ACSs in cancer treatment is summarized.

Roles of vitamin A in the regulation of fatty acid synthesis

Dietary macronutrients and micronutrients play important roles in human health.On the other hand,the excessive energy derived from food is stored in the form of triacylglycerol.A variety of dietary and hormonal factors affect this process through the regulation of the activities and expression levels of those key player enzymes involved in fatty acid biosynthesis such as acetyl-CoA carboxylase,fatty acid synthase,fatty acid elongases,and desaturases.As a micronutrient,vitamin A is essential for the health of humans.Recently,vitamin A has been shown to play a role in the regulation of glucose and lipid metabolism.This review summarizes recent research progresses about the roles of vitamin A in fatty acid synthesis.It focuses on the effects of vitamin A on the activities and expression levels of mRNA and proteins of key enzymes for fatty acid synthesis in vitro and in vivo.It appears that vitamin A status and its signaling pathway regulate the expression levels of enzymes involved in fatty acid synthesis.Future research directions are also discussed.

Impact of Chain Length of Saturated Fatty Acids during Their Heterogeneously Catalyzed Deoxygenation

Fatty acids with different chain length were deoxygenated in the absence of hydrogen (caprylic acid (CA), lauric acid (LA) and stearic acid (SA)). The catalytic tests were carried over Pd-containing catalysts out in a batch reactor under inert gas for 6 h at 250&degC to 350&degC and pressures from 18 to 75 bar in the absence of additionally fed hydrogen. Pd-containing catalysts were tested;the best performing catalyst was 10% Pd/C with 63% undecane yield at 327&degC. These catalysts were used for a comparative decarboxylation of CA, LA and SA. At equal reaction conditions (300&degC, 6 h), the chain length of the fatty acid had a strong impact on the conversion, which was steadily increasing, whereas the alkane selectivity ran through a maximum. This work demonstrated the usability of Pd-containing catalysts for the decarboxylation of various fatty acids in the absence of additionally fed hydrogen with respect to the manufacture of hydrocarbons that can be used as blending components for fuels.

Cloning of fatty acid elongase1 gene and molecular identification of A and C genome in Brassica species

The fatty acid elongase 1 (FAE1) genes of Brassic napus were cloned from two cultivars, i.e. Zhong- shuan No. 9 with low erucic acid content, and Zhongyou 821 with high erucic acid content, using the degenerate PCR primers. The sequence analysis showed that there was no intron within the FAE1 genes. The FAE1 genes from Zhongyou 821 contained a coding sequence of 1521 nucleotides, and those cloned from Zhongshuan No. 9 contained a 1517 bp coding sequence. Alignment of the FAE1 sequences from Brassica rapa, B. oleracea and B. napus detected 31 single nucleotide polymorphic sites (2.03%), which resulted in 7 amino-acid substitutions. Further analysis indicated that 19 SNPs were genome-specific, of which, 95% were synonymous mutations. The nucleotide substitution at po- sition 1217 in the FAE1 genes led to a specific site of restricted cleavage. An AvrII cleavage site was present only in the C genome genes and absent in the A genome FAE1 genes. Digestion profile of the FAE1 sequences from B. rapa, B. oleracea and B. napus produced with AvrII confirmed that the FAE1 genes of B. oleracea origin was recognized and digested, while that of B. rapa origin could not. The results indicated that by AvrII cleavage it was possible to distinguish B. rapa from B. oleracea and be- tween the A and C genome of B. napus. In addition, the FAE1 genes could be used as marker genes to detect the pollen flow of B. napus, thus providing an alternative method for risk assessment of gene flow.

富里酸诱导对三角褐指藻EPA合成积累的影响

探究不同富里酸质量浓度对三角褐指藻二十碳五烯酸(EPA)合成积累的影响。结果表明,在质量浓度20 mg/L富里酸诱导下,三角褐指藻EPA含量和产量均达到最大值,为19.81 g/100 g和738.91 mg/L,较无富里酸诱导EPA含量和产量分别提高1.12和1.50倍。外源富里酸作用提高了三角褐指藻胞内过氧化物酶(POD)、超氧化物歧化酶(SOD)、过氧化氢酶(CAT)的酶活,使色素(叶绿素、类胡萝卜素)和总多酚抗氧化组分比例增加,活性氧(ROS)和丙二醛(MDA)水平降低,整体抗氧化能力获得显著提升,有效阻抑EPA的氧化分解;富里酸作用同时还上调了EPA合成通路去饱和酶(Δ^(5)-FADS、Δ^(6)-FADS、Δ^(12)-FADS、Δ^(15)-FADS、Δ^(17)-FADS)和延长酶(Δ^(6)-ELOVL)等系列关键酶,使其上调表达量较无富里酸作用分别增加0.33、0.94、0.33、0.58、1.15和0.70倍,为EPA高效合成积累提供前驱物和能量。

不同超长链脂肪酸延长酶基因FAE1芥酸合成功能的比较

植物芥酸是在以FAE1(Fatty acid elongase 1)编码的β-酮脂酰-CoA合酶为关键限速酶的多酶复合体的催化下合成的,主要以TAG形式储存于种子中,是一种重要的油脂化工原料。不同植物来源的FAE1基因序列差异是导致其芥酸合成能力差异的根本原因。为分离和鉴定芥酸高合成能力的FAE1,本研究采用同源克隆法从油菜、海甘蓝、旱金莲和荷包蛋花等4种植物中克隆获得了12条正常编码的FAE1基因序列,并分别构建表达载体在酵母中进行诱导表达和芥酸含量比较分析。结果表明,源于不同植物的12条FAE1基因cDNA序列一致性介于52.1%~99.9%,氨基酸序列一致性介于49.9%~99.8%,FAE1基因具有明显的种属特性。酵母表达及GC-MS分析结果表明,源于绵油328、海甘蓝和荷包蛋花的8个FAE1基因具有超长链脂肪酸合成能力,其中CaFAE1-3合成芥酸能力最强(4.82%),其次为GjFAE1-1(4.53%),LdFAE1合成芥酸能力最弱(0.29%);CaFAE1-3对C20∶1转化率可达95.39%,在高芥酸育种领域具有极大的应用潜力。另外4个源自阳光80和旱金莲的FAE1基因均不具有芥酸合成功能,因为GyFAE1-2、TmFAE1-1和TmFAE1-2在保守的半胱氨酸或(和)组氨酸位点存在突变,而GyFAE1-1存在1个R395K突变,导致酶活丧失。本研究增进了对FAE1基因结构与功能之间关系的认识,为油菜和海甘蓝的高芥酸育种及芥酸性状基因工程改良提供了科学依据。

Acyl-CoA synthase ACSL4:an essential target in ferroptosis and fatty acid metabolism

Long-chain acyl-coenzyme A(CoA)synthase 4(ACSL4)is an enzyme that esterifies CoA into specific polyunsaturated fatty acids,such as arachidonic acid and adrenic acid.Based on accumulated evidence,the ACSL4-catalyzed biosynthesis of arachidonoyl-CoA contributes to the execution of ferroptosis by triggering phospholipid peroxidation.Ferroptosis is a type of programmed cell death caused by iron-dependent peroxidation of lipids;ACSL4 and glutathione peroxidase 4 positively and negatively regulate ferroptosis,respectively.In addition,ACSL4 is an essential regulator of fatty acid(FA)metabolism.ACSL4 remodels the phospholipid composition of cell membranes,regulates steroidogenesis,and balances eicosanoid biosynthesis.In addition,ACSL4-mediated metabolic reprogramming and antitumor immunity have attracted much attention in cancer biology.Because it facilitates the cross-talk between ferroptosis and FA metabolism,ACSL4 is also a research hotspot in metabolic diseases and ischemia/reperfusion injuries.In this review,we focus on the structure,biological function,and unique role of ASCL4 in various human diseases.Finally,we propose that ACSL4 might be a potential therapeutic target.

海洋破囊壶菌Thraustochytrium sp．FJN-10 DHA生物合成途径相关延长酶的克隆与表达

二十二碳六烯酸(Docosahexaenoic acid,DHA)是具有各种重要生理功能的高度不饱和脂肪酸。以海洋真菌Thraustochytrium sp.FJN-10为研究对象,利用RT-PCR结合RACE,获得了两个碳链延长酶(TFD6和TFD5)的完整基因,其中TFD6 cDNA全长816 bp,编码271个氨基酸;TFD5 cDNA全长831 bp,编码276个氨基酸。将TFD6、TFD5酶切后分别连接到HindⅢ/XbaⅠ处理过的pYES2载体,醋酸锂法转化酿酒酵母感受态细胞,成功构建了延长酶酵母表达系统。气相色谱分析表明TFD6可延长C18:3n-6至C20:3n-6,TFD5可延长C20:5n-3至C22:5n-3。

草鱼脂肪酸去饱和酶和延长酶基因cDNA全序列的克隆与分析

利用RT-PCR和RACE方法克隆得到草鱼(Ctenopharyngodon idellus)肝脏中控制高不饱和脂肪酸(HU-FA)合成的脂肪酸去饱和酶(FAD)和脂肪酸延长酶(ELO)基因cDNA全序列.结果表明,草鱼FAD基因cDNA全长为1 994 bp,开放阅读框(ORF)为1 332 bp,编码444个氨基酸.编码的蛋白序列包含FAD全部特征结构区,包括3个组氨酸簇、2个跨膜区和1个细胞色素b5结构域,与其他鱼类的FAD氨基酸序列具有63.5%～70.5%的同源性.通过系统树分析,显示其在系统树中与草食性淡水鱼的亲缘关系最近.克隆得到的草鱼ELO的全长cDNA序列1 131 bp,含有876 bp的ORF,编码291个氨基酸.该蛋白序列含有单一的氧化还原中心组氨酸簇、内质网停留信号和多个跨膜区等ELO特征结构,与其他类别ELO氨基酸具有70.6%～89.3%的同源性.系统树分析显示其在系统树中与草食性和杂食性淡水鱼类亲缘关系较近.草鱼FAD和ELO cDNA全序列的获得为今后进一步研究其体内高不饱和脂肪酸合成途径及阐明该途径在不同鱼类中的分子进化机理奠定基础.