共查询到19条相似文献,搜索用时 171 毫秒
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鱼油的主要成分为二十碳五烯酸和二十二碳六烯酸,这些多不饱和脂肪酸具有多方面的生理活性。近年来在海洋细菌中发现这些多不饱和脂肪酸的存在,海洋细菌很可能是这些多不饱和脂肪酸的原始生产之一。对其生物合成的深入研究表明,海洋细菌多不饱和脂肪酸的合成不同于其他生物的不饱和脂肪酸的合成机制,合成过程中不涉及重要的脂肪酸脱氢和延长机制,其合成由一种多聚乙酰合成酶(PKS)催化。 相似文献
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聚羟基脂肪酸酯(Polyhydroxyalkanoates,PHA)是许多细菌在非平衡生长条件下在胞内积累的以颗粒状态存在的碳源和能源储藏物质。PHA因其具有生物可降解性、生物相容性等许多良好的材料性质、可以作为化学合成塑料未来的替代品而引起广泛关注。但由短链脂肪酸或单一脂肪酸单体合成的PHA的材料性质具有局限性,需要利用多种单体合成满足实际需求的PHA材料。PHA合成酶的底物特异性和PHA合成代谢途径决定着PHA的单体组成情况,进而影响着PHA的理化特性和材料性能。因此需要对PHA合成酶进行改造,扩展其对底物的特异性。另一方面需要构建新的PHA合成代谢途径,能合成出一些不常见的且性能优良的PHA材料。综述了近些年对PHA合成酶改造的研究及PHA代谢途径构建的研究进展。 相似文献
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海生杆菌属首次于1997年鉴定,迄今包括18个物种,其中10个已完成全基因组序列测定。文中总结了海生杆菌属的菌种特征,并从碳源利用、聚羟基脂肪酸酯代谢和芳香族化合物降解三个方面对基因组测序数据进行了分析。研究发现,海生杆菌属具有完整的糖酵解途径和三羧酸循环,缺乏木糖利用基因。所有海生杆菌属菌种均含有Ⅰ型和Ⅲ型聚羟基脂肪酸酯合成酶的编码基因,表明该菌属可能具有普遍的聚羟基脂肪酸酯合成能力。海生杆菌属含有芳香族化合物的降解途径,苯、苯酚和苯甲酸可由不同的酶催化生成邻苯二酚,再由邻位断裂途径降解为3-酮己二酸,邻苯二酚也可由间位断裂途径降解为丙酮酸和乙酰辅酶A。基因组测序数据分析加深了对海生杆菌属代谢特征的认识,提示该菌属在聚羟基脂肪酸酯合成和海洋芳香族污染物治理方面有一定的应用前景。 相似文献
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不同细菌来源的3-酮脂酰ACP合成酶Ⅲ生物学特性分析 总被引:1,自引:0,他引:1
3-酮脂酰ACP合成酶Ⅲ(FabH)是催化细菌脂肪酸合成的起始反应.研究表明,革兰氏阳性细菌FabH对支链脂酰-CoA前体的选择性是其合成支链脂肪酸的关键.但部分革兰氏阴性细菌也产生一定量的支链脂肪酸,其合成机制还不清楚.为此,本研究选取了革兰氏阳性细菌枯草芽孢杆菌BsfabH1和BsfabH2、金黄色葡萄球菌SafabH、天蓝色链霉菌ScofabH、革兰氏阴性细菌茄科雷尔氏菌RsfabH、大肠杆菌EcfabH,以及产支链脂肪酸的水稻黄单胞菌XoofabH,共7种fabH同源基因进行生物学特性分析.异体遗传互补茄科雷尔氏菌fabH突变株RsmH,表明这7个基因编码蛋白都具有3-酮脂酰ACP合成酶Ⅲ活性.脂肪酸组成分析显示,4个革兰氏阳性菌fabH和XoofabH互补株类似,均能产生支链脂肪酸,而EcfabH和RsfabH互补株不产生支链脂肪酸,说明XooFabH不同于EcFabH,参与支链脂肪酸合成.体外酶学分析表明,XooFabH与4种革兰氏阳性菌FabH类似,对支链脂酰-CoA有较高的选择,但EcFabH和RsFabH对支链前体活性低.与革兰氏阳性细菌FabH不同,XooFabH对中短链长(C4~C10)脂酰-CoA也具有较高的活性.综合以上结果,不同细菌来源FabH的生物学特性差异明显,FabH能利用支链前体是细菌合成支链脂肪酸的关键因素. 相似文献
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磷酸泛酰巯基乙胺基转移酶(phosphopantetheinyl transferases,PPTase)可催化脂肪酸合酶(fatty acid synthases,FAS)、聚酮合成酶(polyketide synthases,PKS)以及非核糖体肽合成酶(non-ribosomal peptide syntethases,NRPS)的酰基载体蛋白(acyl carrier protein,ACP)及肽酰载体蛋白(peptidyl carrier protein,PCP)等的翻译后修饰反应,将辅酶A(coenzyme A,CoA)上的磷酸泛酰巯基乙胺基转移到ACP及PCP的保守丝氨酸残基上,从而激发ACP及PCP的活性,由此脂肪酸、聚酮、非核糖体肽得以合成。在大部分真菌及细菌中都存在着PPTase,且其在生物代谢中起到重要的作用。现对其研究进展进行阐述。 相似文献
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具有广泛生物活性的真菌聚酮化合物因具有复杂的化学结构,其生物合成途径一般包含多样且新颖的酶催化反应。文中主要综述了2013-2016年来源于还原性聚酮合成酶(HR-PKSs)、非还原性聚酮合成酶(NR-PKSs)、聚酮-非核糖体多肽合成酶(PKS-NRPSs)和还原性-非还原性聚酮合成酶(HR-NR PKSs)杂合型等四大类型的真菌聚酮类化合物的生物合成研究进展。众多真菌聚酮类化合物生物机理的阐明,为未来新型真菌聚酮类天然产物生物合成基因簇的挖掘、新结构化合物的发现及其类似物的研究提供了方向和理论基础。 相似文献
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Plumbing the depths of PUFA biosynthesis: a novel polyketide synthase-like pathway from marine organisms 总被引:6,自引:0,他引:6
Napier JA 《Trends in plant science》2002,7(2):51-54
Polyunsaturated fatty acids (PUFAs) are involved in determining the biophysical properties of membranes as well as being precursors for signalling molecules. C(20+) PUFA biosynthesis is catalysed by sequential desaturation and fatty acyl elongation reactions. This aerobic biosynthetic pathway was thought to be taxonomically conserved, but an alternative anaerobic pathway for the biosynthesis of polyunsaturated fatty acids is now known to exist that is analogous to polyketide synthases (PKS). These novel PKS genes could be used to direct the synthesis of PUFAs in heterologous hosts, as well as exploiting the combinatorial chemistry of PKSs to make unusual fatty acids. 相似文献
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Matsuda T Sakaguchi K Hamaguchi R Kobayashi T Abe E Hama Y Hayashi M Honda D Okita Y Sugimoto S Okino N Ito M 《Journal of lipid research》2012,53(6):1210-1222
Thraustochytrids are known to synthesize PUFAs such as docosahexaenoic acid (DHA). Accumulating evidence suggests the presence of two synthetic pathways of PUFAs in thraustochytrids: the polyketide synthase-like (PUFA synthase) and desaturase/elongase (standard) pathways. It remains unclear whether the latter pathway functions in thraustochytrids. In this study, we report that the standard pathway produces PUFA in Thraustochytrium aureum ATCC 34304. We isolated a gene encoding a putative Δ12-fatty acid desaturase (TauΔ12des) from T. aureum. Yeasts transformed with the tauΔ12des converted endogenous oleic acid (OA) into linoleic acid (LA). The disruption of the tauΔ12des in T. aureum by homologous recombination resulted in the accumulation of OA and a decrease in the levels of LA and its downstream PUFAs. However, the DHA content was increased slightly in tauΔ12des-disruption mutants, suggesting that DHA is primarily produced in T. aureum via the PUFA synthase pathway. The transformation of the tauΔ12des-disruption mutants with a tauΔ12des expression cassette restored the wild-type fatty acid profiles. These data clearly indicate that TauΔ12des functions as Δ12-fatty acid desaturase in the standard pathway of T. aureum and demonstrate that this thraustochytrid produces PUFAs via both the PUFA synthase and the standard pathways. 相似文献
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Bacterial production of long-chain omega-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), is constrained to a narrow subset of marine γ-proteobacteria. The genes responsible for de novo bacterial PUFA biosynthesis, designated pfaEABCD, encode large, multi-domain protein complexes akin to type I iterative fatty acid and polyketide synthases, herein referred to as "Pfa synthases". In addition to the archetypal Pfa synthase gene products from marine bacteria, we have identified homologous type I FAS/PKS gene clusters in diverse microbial lineages spanning 45 genera representing 10 phyla, presumed to be involved in long-chain fatty acid biosynthesis. In total, 20 distinct types of gene clusters were identified. Collectively, we propose the designation of "secondary lipids" to describe these biosynthetic pathways and products, a proposition consistent with the "secondary metabolite" vernacular. Phylogenomic analysis reveals a high degree of functional conservation within distinct biosynthetic pathways. Incongruence between secondary lipid synthase functional clades and taxonomic group membership combined with the lack of orthologous gene clusters in closely related strains suggests horizontal gene transfer has contributed to the dissemination of specialized lipid biosynthetic activities across disparate microbial lineages. 相似文献
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Miku Matsuzawa 《Phytochemistry》2010,71(10):1059-306
Alkylresorcinols, produced by various plants, bacteria, and fungi, are bioactive compounds possessing beneficial activities for human health, such as anti-cancer activity. In rice, they accumulate in seedlings, contributing to protection against fungi. Alkylresorcylic acids, which are carboxylated forms of alkylresorcinols, are unstable compounds and decarboxylate readily to yield alkylresorcinols. Genome mining of the rice Oryza sativa identified two type III polyketide synthases, named ARAS1 (alkylresorcylic acid synthase) and ARAS2, that catalyze the formation of alkylresorcylic acids. Both enzymes condensed fatty acyl-CoAs with three C2 units from malonyl-CoA and cyclized the resulting tetraketide intermediates via intramolecular C-2 to C-7 aldol condensation. The alkylresorcylic acids thus produced were released from the enzyme and decarboxylated non-enzymatically to yield alkylresorcinols. This is the first report on a plant type III polyketide synthase that produces tetraketide alkylresorcylic acids as major products. 相似文献
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The disposal and more efficient utilization of marine wastes is becoming increasingly serious. A culture media for microorganisms has been prepared from squid internal organs that are rich in polyunsaturated fatty acids (PUFAs). Both freshwater and marine bacteria grew well in this medium and some bacteria accumulated PUFAs in their lipids, suggesting uptake of exogenous PUFAs. Higher PUFA accumulations were observed in Escherichia coli mutant cells defective either in unsaturated fatty acid biosynthesis or fatty acid degradation, or both, compared to those without these mutations. Therefore, PUFA accumulation in cells can be improved by genetic modification of fatty acid metabolism in the bacteria. Squid internal organs would be a good source of medium, not only for marine bacteria but also for freshwater bacteria, and that this process may be advantageous to make efficient use of the fishery wastes and to produce PUFA-containing microbial cells and lipids. 相似文献
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《Journal of lipid research》2023,64(9):100361
N-acyl taurines (NATs) are bioactive lipids with emerging roles in glucose homeostasis and lipid metabolism. The acyl chains of hepatic and biliary NATs are enriched in polyunsaturated fatty acids (PUFAs). Dietary supplementation with a class of PUFAs, the omega-3 fatty acids, increases their cognate NATs in mice and humans. However, the synthesis pathway of the PUFA-containing NATs remains undiscovered. Here, we report that human livers synthesize NATs and that the acyl-chain preference is similar in murine liver homogenates. In the mouse, we found that hepatic NAT synthase activity localizes to the peroxisome and depends upon an active-site cysteine. Using unbiased metabolomics and proteomics, we identified bile acid-CoA:amino acid N-acyltransferase (BAAT) as the likely hepatic NAT synthase in vitro. Subsequently, we confirmed that BAAT knockout livers lack up to 90% of NAT synthase activity and that biliary PUFA-containing NATs are significantly reduced compared with wildtype. In conclusion, we identified the in vivo PUFA-NAT synthase in the murine liver and expanded the known substrates of the bile acid-conjugating enzyme, BAAT, beyond classic bile acids to the synthesis of a novel class of bioactive lipids. 相似文献
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Characterization of Cyanobacterial Hydrocarbon Composition and Distribution of Biosynthetic Pathways
R. Cameron Coates Sheila Podell Anton Korobeynikov Alla Lapidus Pavel Pevzner David H. Sherman Eric E. Allen Lena Gerwick William H. Gerwick 《PloS one》2014,9(1)
Cyanobacteria possess the unique capacity to naturally produce hydrocarbons from fatty acids. Hydrocarbon compositions of thirty-two strains of cyanobacteria were characterized to reveal novel structural features and insights into hydrocarbon biosynthesis in cyanobacteria. This investigation revealed new double bond (2- and 3-heptadecene) and methyl group positions (3-, 4- and 5-methylheptadecane) for a variety of strains. Additionally, results from this study and literature reports indicate that hydrocarbon production is a universal phenomenon in cyanobacteria. All cyanobacteria possess the capacity to produce hydrocarbons from fatty acids yet not all accomplish this through the same metabolic pathway. One pathway comprises a two-step conversion of fatty acids first to fatty aldehydes and then alkanes that involves a fatty acyl ACP reductase (FAAR) and aldehyde deformylating oxygenase (ADO). The second involves a polyketide synthase (PKS) pathway that first elongates the acyl chain followed by decarboxylation to produce a terminal alkene (olefin synthase, OLS). Sixty-one strains possessing the FAAR/ADO pathway and twelve strains possessing the OLS pathway were newly identified through bioinformatic analyses. Strains possessing the OLS pathway formed a cohesive phylogenetic clade with the exception of three Moorea strains and Leptolyngbya sp. PCC 6406 which may have acquired the OLS pathway via horizontal gene transfer. Hydrocarbon pathways were identified in one-hundred-forty-two strains of cyanobacteria over a broad phylogenetic range and there were no instances where both the FAAR/ADO and the OLS pathways were found together in the same genome, suggesting an unknown selective pressure maintains one or the other pathway, but not both. 相似文献
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The role of polyunsaturated fatty acids (PUFAs) in inflammatory lesions of the intestines is the subject of increasing research. This review begins with a background discussion of the source, elongation, and desaturation of PUFAs, as well as the role they have played in the human diet through evolution. The available data and hypotheses as to how manipulation of PUFAs might effect the various components of the immune system are then provided. Possible mechanisms by which PUFAs result in immunomodulation include alterations in eicosanoid synthesis, membrane fluidity, signal transduction, intraluminal bacteria, and gene expression. Attention is then turned to the known effects that these polyunsaturated fatty acids have on the various individual components of the immune system including lymphocytes, neutrophils, and antigen presenting cells, as well as the immunoregulatory process of apoptosis. Finally, laboratory data on the role of PUFAs in necrotizing enterocolitis, and to a greater extent inflammatory bowel disease, first as demonstrated in animal models of the disease, and second in human studies are then summarized. 相似文献