Gut Dysbiosis during Influenza Contributes to Pulmonary Pneumococcal Superinfection through Altered Short-Chain Fatty Acid Production

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无溶剂体系中脂肪酶改造猪油制备功能性脂的研究

我国有丰富廉价的动植物油资源,但这一资源并未得到有效的利用,为了充分利用这些资源,开展了无溶剂系统脂肪酶催化猪油与辛酸酸解制备功能性脂的研究工作。脂肪酶筛选实验表明,在所选用的五种脂肪酶中,来自T .languginosa的固定化脂肪酶LiopzymeTLIM的催化效果最好。以LipozymeTLIM为催化剂,进一步研究了酶量、底物比率、反应时间、反应温度和水分添加量对猪油中辛酸插入率的影响。反应产物通过高效液相色谱法(HPLC)进行分析。研究结果表明,当脂肪酶量为20% (底物重量百分比)时,猪油中辛酸插入率最高。反应时间研究表明,当反应时间达到24h时,辛酸的插入率最高,达到38.77mol%。当猪油与辛酸的比率为1∶2 (摩尔比)时,辛酸的插入率最高,达到30 95mol%。在4 5～6 0℃范围之内,反应温度对辛酸插入率没有明显的影响,温度高于6 0℃时,辛酸插入率降低。水分添加量为2 5 %时,辛酸插入率最高,高达35 76mol%。     

Precision Microbiome Modulation with Discrete Dietary Fiber Structures Directs Short-Chain Fatty Acid Production

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Treatment of Candida Rugosa Lipase with Short-Chain Polar Organic Solvents Enhances its Hydrolytic and Synthetic Activities

Following a simple and quick treatment based on dissolving the crude lipase from Candida rugosa in different percentages (v/v) of several polar organic solvents (methanol, ethanol, 1 and 2-propanol, 1 and 2-butanol and acetone) followed by dialysis, different preparations with enhanced activities were obtained. The opening of the lid covering the active site is proposed as the reason for explaining the activity enhancement, both in aqueous and anhydrous organic media.     

Inhibition of the Acid Lipase Activity by Apolipoprotein A-I in the Presence of Lysosomal Proteases

It was found that the inhibition of the lysosomal acid lipase activity by rat apolipoprotein A-I (apo A-I) was increased with the degradation of apo A-I by the lysosomal proteases. We demonstrated that apo A-I could effectively inhibit the acid lipase activity even in the presence of the lysosomal proteases using the hepatic lysosomal fraction.     

Acid Lipase Inhibitor in Chicken Plasma Identified as Apolipoprotein A-I

We have reported a inhibitor of acid lipases in liver lysosomes and erythrocytes from chickens [M. Fujii et al., Int. J. Biochem., 22, 895–898 (1990)]. In this paper, the properties of the inhibitor were described in comparison with those of apo A-I of chicken.

The purified inhibitor migrated with the same mobility on SDS–PAGE as apo A-I, and had a molecular weight of 27,000. The peptide map from the lipase inhibitor was similar to that of apo A-I. Antibodies to the acid lipase inhibitor also reacted with apo A-I. Apo A-I inhibited the acid lipase activities of liver lysosomes and erythrocytes from chickens as strongly as the lipase inhibitor. The N-terminal amino acid sequence of lipase inhibitor was identical to that of apo A-I as far as residue 20. The amino acid sequence of peptides obtained from the inhibitor by cleavage with CNBr corresponded to internal sequence of apo A-I, and so the CNBr-peptides were derived by cleavage after the methionine residues in apo A-I. The findings showed that the inhibitor of the acid lipases in liver lysosomes and erythrocytes from chickens was identical to apo A-I.     

The Influence of Fatty Acid and Glycerol on the Kinetics of Fat Hydrolysis by Candida Rugosa Lipase in a Membrane Reactor

The kinetics of lipid-hydrolysis by Candida rugosa lipase was investigated in a membrane reactor and in an emulsion system. Two models were chosen to describe the kinetics of the enzyme:

(1) The hydrolysis of triglycerides to fatty acids was considered to be a chain reaction with the intermediary products di- and mono-glyceride; each step was assumed to be a reversible second-order reaction. The reaction rate constants were determined from batch experiments. The experimental results could be described with this model.

(2) For process optimization and control, a model based on the power law was developed. For this model, the rate of hydrolysis was measured as a function of fatty acid and glycerol concentrations. Relations for the initial rate and equilibrium ester fraction as a function of the glycerol concentration were determined. Further, the reaction rate could be described with the power-law model with a power of 1.75 in the hydrolyzable ester fraction for a wide range of glycerol concentrations. The model with power 1.75 gave much better results when compared to a similar first order model. Although simpler, the first order model can not be used. The power law model was applied in the simulation of a reactor composed of three modules. The fatty acid production rate was calculated for this reactor system as a function of the outgoing glycerol concentration at different conditions.     

The role of short-chain fatty acids in the interplay between diet,gut microbiota,and host energy metabolism

Short-chain fatty acids (SCFAs), the end products of fermentation of dietary fibers by the anaerobic intestinal microbiota, have been shown to exert multiple beneficial effects on mammalian energy metabolism. The mechanisms underlying these effects are the subject of intensive research and encompass the complex interplay between diet, gut microbiota, and host energy metabolism. This review summarizes the role of SCFAs in host energy metabolism, starting from the production by the gut microbiota to the uptake by the host and ending with the effects on host metabolism. There are interesting leads on the underlying molecular mechanisms, but there are also many apparently contradictory results. A coherent understanding of the multilevel network in which SCFAs exert their effects is hampered by the lack of quantitative data on actual fluxes of SCFAs and metabolic processes regulated by SCFAs. In this review we address questions that, when answered, will bring us a great step forward in elucidating the role of SCFAs in mammalian energy metabolism.     

肌肉脂肪酸转运膜蛋白及其相互关系

肌肉（骨骼肌）组织对脂肪酸的利用水平是影响机体能量稳态的关键因素.肌肉摄取的长链脂肪酸(long chain fatty acids,LCFAs)主要依赖细胞膜载体蛋白协助的跨膜转运过程.近年来,一系列与脂肪酸转运相关的膜蛋白被相继克隆鉴定,其中在肌肉中大量表达的有脂肪酸转运蛋白-1（fatty acid transport protein-1,FATP-1）、膜脂肪酸结合蛋白（plasma membrane fatty acid binding protein,FABPpm）、脂肪酸转位酶（fatty acid translocase,FAT/CD36）和小窝蛋白-1（caveolin-1）.研究上述肌肉脂肪酸转运膜蛋白的结构功能、调控机制及相互关系,可能为肥胖等脂类代谢紊乱疾病的诊治提供新的手段.     

Purification of Stearidonic Acid (18:4(n-3)) and Hexadecatetraenoic Acid (16:4(n-3)) from Algal Fatty Acid with Lipase and Medium Pressure Liquid Chromatography

Stearidonic acid (18:4(n-3)) and hexadecatetraenoic acid (16:4(n-3)) are included in some edible marine algae such as Undaria pinnatifida and Ulva pertusa with relatively high compositions (up to 40%) of total fatty acids. In order to prepare 16:4(n-3) and 18:4(n-3) enriched fatty acid concentrates, we screened for a suitable lipase which concentrates these acids by the removal of other fatty acids in the selective esterification reaction reported by Shimada et al. (Shimada et al. (1997), J. Am. Oil Chem. Soc., 74, 1465-1470). In combination with the lipase reaction and reversed-phase medium pressure liquid chromatography, we purified 18:4(n-3) and 16:4(n-3) to more than 95% purity.     

Inhibition of Membrane-Active Peptides by Fatty Acid–Peptide Hybrids

Nine fatty acid–peptide hybrid molecules were constructed using the general formula CH₃(CH₂) _n CO-Phe Asp Cys-amide and tested for their ability to inhibit cell lysis induced by the membrane-active peptide melittin. All of these molecules, where n = 4–14, inhibited the action of melittin to some extent, but the longer carbon chains were most effective. Several potential inhibitors were also constructed with conservative substitutions in the peptide portion of the molecule. All were effective to varying degrees. We concluded that in the hexapeptide inhibitor published by Blondelle et al. (1993), the role of the first three residues is only to provide hydrophobic interaction with the melittin and has no particular amino acid sequence specificity. Some of these inhibitors were found to inhibit the lytic activity of a melittin analogue which had only superficial sequence similarity to melittin and also a truncated form of melittin, indicating the generality of the action of the inhibitors.Deceased 5/4/98     

Effect of Short-Chain Fatty Acids and Soil Atmosphere on Tylenchorhynchus spp.

Short-chain fatty acids can be produced under anaerobic conditions by fermentative soil microbes and have nematicidal properties. We evaluated the effects of butyric and propionic acids on death and recovery of stunt nematodes (Tylenchorhynchus spp.), a common parasite of turfgrass. Nematodes in a sand-soil mix (80:20) were treated with butyric or propionic acid and incubated under air or N₂ for 7 days at 25 °C. Amendment of soil with 0.1 and 1.0 µmol (8.8 and 88 µg) butyric acid/g soil or 1.0 µmol (74 µg) propionic acid/g soil resulted in the death of all nematodes. The composition of the soil atmosphere had no effect on the nematicidal activity of the acids. Addition of hydrochloric acid to adjust soil pH to 4.4 and 3.5 resulted in nematode mortality relative to controls (41% to 86%) but to a lesser degree than short-chain fatty acids at the same pH. Nematodes did not recover after a 28-day period following addition of 10 µmol butyric acid/g soil under air or N₂. Carbon mineralization decreased during this period, whereas levels of inorganic N and microbial biomass-N remained constant. Short-chain fatty acids appear to be effective in killing Tylenchorhynchus spp. independent of atmospheric composition. Nematode mortality appears to be a function of the type and concentration of fatty acid and soil pH.     

Polyethylene Glycol-Modified Lipase Soluble and Active in Organic Solvents

A new approach in biotechnological processes is to use lipase modified with polyethylene glycol(PEG) which has both hydrophilic and hydrophobic properties. The PEG-lipase is soluble in organic solvents such as benzene and chlorinated hydrocarbons and exhibits high enzymic activity in organic solvents. The PEG-lipase catalyses the reverse reaction of hydrolysis in organic solvents; ester synthesis and ester exchange reactions. The PEG-lipase can also be conjugated to magnetite (Fe₃O₄). The magnetic lipase catalyses ester synthesis in organic solvents and can be readily recovered by magnetic force without loss of enzymic activity.     

脂肪酸脱饱和酶的研究进展

脂肪酸脱饱和酶催化与载体结合的饱和脂肪酸或不饱和脂肪酸在脂酰链上形成双键。脂肪酸脱饱和酶分为脂酰ＣｏＡ脱饱和酶、脂酰ＡＣＰ脱饱和酶和脂酰脂脱饱和酶三类。它在控制生物膜的形成与物理性质,保护光合机构和决定贮脂与膜脂的脂肪酸组成与不饱和度等方面起着关键作用。     

有机相中酶促有机硅烷醇的转酯

在有机介质中,脂肪酶L-1754可以催化非天然有机硅烷醇与脂肪酸酯的转酯反应.反应介质、反应体系水活度和底物的结构对酶促转酯反应有显著的影响.适宜的反应介质为正辛烷,反应体系最适水活度为0.55.     

Kinetics of Enantioselective Esterification of Naproxen by Lipase in Organic Solvents

The kinetics of stereoselective esterification of racemic Naproxen with trimethylsilyl methanol by Candida cylindracea lipase in organic solvents has been investigated. A Ping-Pong Bi Bi mechanism with competitive inhibition by this alcohol for each enantiomer -has been identified. The rate equations were further analyzed in the time-course reaction after considering the effect of enzyme deactivation in the organic mixtures, but not in isooctane. Effects of the hydrophobicity of solvent on the solubility of the racemate, the kinetic parameters and their combinations are also discussed.     

Free Fatty Acid Composition of Human and Rat Peripheral Nerve

Abstract: The free fatty acid (FFA) composition of peripheral nerve resembles that of erythrocytes but the composition of both is different from that of brain and other tissues. Approximately 75% of FFAs of nerve and erythrocytes are saturated and <5% are polyunsaturated whereas in brain and other tissues, 30-45% of FFAs are saturated and 25-50% are polyunsaturated. Approximately 10-15% of the total FFA of nerve have very long chain lengths [C₂₄, C₂₆, C₂₈, and C₃₀]. The presence of these very long-chain FFAs in endoneurium cannot be accounted for by the retention of erythrocytes or by lipid degradation. During Wallerian degeneration a significant increase of 18:1, associated with a decrease of saturated FFAs, was found in rat sciatic endoneurium, but normal values were approached when fiber regeneration was well under way. The FFA composition with chain length ≥C₂₆ were not, however, significantly altered with degeneration or repair of nerves. The metabolic significance of this striking difference between nerve and brain FFA composition is unknown but may reflect different functional properties.     

Arachidonic Acid Liberated by Diacylglycerol Lipase Is Essential for the Release Mechanism in Chromaffin Cells from Bovine Adrenal Medulla

Chromaffin cells from bovine adrenal medulla secrete catecholamines on stimulation with acetylcholine. In addition to the activation of the phosphatidylinositol cycle, arachidonic acid is generated, which was thought to be the result of phospholipase A2 activation. We have demonstrated in isolated plasma membranes of these cells that arachidonic acid is generated by a two-step reaction of diacylglycerol and monoacylglycerol lipase splitting diacylglycerol, which originates from the action of phospholipase C on phosphatidylinositols. No phospholipase A2 activity could be detected in plasma membranes so far. External addition of arachidonic acid increases the release in the absence and in the presence of agonist. Inhibition of the diacylglycerol lipase by RHC 80267 suppresses the catecholamine release, which is restored on addition of arachidonic acid. This effect, however, is reversed by lipoxygenase inhibitors, indicating that it is not arachidonic acid itself, but one of its lipoxygenase products, that is essential for inducing exocytosis.     

逆境对真菌膜脂肪酸成分的影响

利用气相色谱对真菌膜脂肪酸在逆境下的变化进行研究,发现低温胁迫时膜上的不饱和脂肪酸较多,低碳源浓度、低氧浓度和高盐浓度胁迫时,膜上不饱和脂肪酸的含量反而出现降低。表明不同逆境胁迫时,真菌中膜的脂肪酸含量不一样。