Replacing soybean meal with microalgae biomass in diets with contrasting carbohydrate profile can reduce in vitro methane production and improve short-chain fatty acids production

The objective of this study was to evaluate the interaction of dietary carbohydrate profile and soybean meal (SBM) replacement with either Chlorella pyrenoidosa (CHL) or Spirulina platensis (SPI) on in vitro fermentation. This experiment was conducted as a randomized complete block design, with fermentation run (3 runs) considered as blocks. The treatments were arranged in a 2 × 5 factorial design, where the first factor was the carbohydrate profile, which was composed of diets containing 42.5% NDF and 26.8% starch (HF-LS) or 26.8% NDF and 40.6% starch (LF-HS) and the second factor was the protein source, in which a control diet (100% SBM), partial replacement of SBM with CHL (1/2 CHL) or SPI (1/2 SPI), or total replacement of SBM with CHL or SPI were used. All experimental diets were formulated to have 17% crude protein. The ruminal fluid was collected from 2 lactating Holstein cows, buffered with Van Soest medium at a ratio of 1:2 and added to serum bottles containing 0.50 g of the experimental diets. Bottles were incubated at 39°C for 24 and 48 h in triplicate; headspace pressure was measured, along with gas collection for methane (CH4) quantification at 0, 2, 4, 8, 16, 24, 36, and 48 h after incubation. The final medium was used to measure pH, ammonia, and volatile-fatty acid (VFA). After incubation, feed bags were recovered and used for estimation of degradability of DMD, NDF, and OMD. Statistical analysis was carried out using the MIXED procedure of SAS, with carbohydrate profile, protein source, assay, and its interactions as fixed effects, with run and bottle as random effects. Orthogonal contrasts were used to compare carbohydrate profile, algae species, carbohydrate profile × algae interaction, and linear and quadratic effects of SBM replacement with CHL or SPI. There was no interaction effect between carbohydrate profile and algae source. LF-HS improved gas production, degradability of nutrients, and VFA, mainly increasing the production of butyrate and propionate. When compared with CHL, SPI had a greater degradability of nutrients and branched VFA, along with reduction in total gas production and tended to reduce total CH4 yield. The replacement of SBM with algae linearly reduced the degradability of nutrients, along with a linear reduction in gas production. When replacement of SBM with only SPI was evaluated, SPI slightly reduced the degradability of nutrients; however, it promoted a linear reduction in CH4 yield, as well as reduction in CH4 yield by unit of degraded DM, NDF, and OM. In summary, there was no interaction of carbohydrate profile and protein source, which means that SBM replacement had a similar effect, regardless of dietary carbohydrate profile. Spirulina may be a more suitable algae source when compared with Chlorella due to the potential to reduce CH4.

Hydrolysed poultry byproduct meal in extruded diets for cats

Hydrolysed proteins have been shown to be potential ingredients in cat diets due to their high digestibility, presence of bioactive peptides, and relatively low antigenicity. The effects of the substitution of conventional low ash poultry byproduct meal (PBM) with hydrolysed poultry byproduct meal (HPM) as a protein source were evaluated in extruded cat diets. Five diets with similar nutrient contents were formulated: a control (CO) diet based on PBM and 4 diets with different inclusions of HPM (5%, 10%, 20%, and 30%, on an as-fed basis) replacing PBM as the protein source. The total tract apparent digestibility (CTTAD) of nutrients, faecal characteristics and microbial fermentation products, urine production and pH, nitrogen balance and urea renal excretion were evaluated using 30 healthy cats (15 males and 15 females; 4.18 ± 0.86 kg; 4.17 ± 1.38 years old), with 6 cats per diet in a complete randomised block design. When significant differences were found with the F test, the effects were evaluated by polynomial contrasts according to HPM inclusion (p < 0.05). The CTTADs of DM (89 ± 0.41%), CP (90 ± 0.36%), fat (93 ± 0.41%) and gross energy (90 ± 0.33%) were similar among treatments (p > 0.05). The faecal production, score, short-chain fatty acids and ammonia concentration were similar among treatments (p > 0.05). Isobutyric, isovaleric, valeric, and total branched-chain fatty acid contents increased quadratically (p < 0.05), with the highest level in the faeces of cats fed the diet with 20% HPM. Lactate concentration in faeces increased linearly with the inclusion of HPM (p < 0.05). Urine characteristics and urea renal excretion did not differ among treatments (p > 0.05). At 10% inclusion, HPM tended to increase the nitrogen retention of cats (p = 0.083), which may reflect the higher tryptophan, methionine, lysine, and available lysine contents of HPM in comparison to PBM. The inclusion of up to 30% HPM can be considered in cat formulations without affecting nutrient digestibility or faecal and urine characteristics. HPM tended to increase nitrogen retention and increased branched-chain fatty acids in faeces, aspects which deserves further studies.

Monomethyl branched-chain fatty acids: Health effects and biological mechanisms

Branched-chain fatty acids (BCFA) are a group of lipids that are widely present in various organisms; they take part in numerous biochemical processes and affect multiple signaling pathways. However, BCFA are not well explored in terms of their effects on human health. Recently, they have been gaining interest, especially in relation to various human diseases. This review describes the occurrence of BCFA, their dietary sources, their potential health effects, and the current state of knowledge concerning their mechanism(s) of action. Many studies have been conducted so far in cellular and animal models, which reveal potent anti-cancer, lipid lowering, anti-inflammatory and neuroprotective actions. Research in humans is scarce. Therefore, further studies on animals and humans should be performed to confirm and expand these findings, and improve our understanding of the potential relevance of BCFA to human health and disease.

Quantification of Very-Long-Chain and Branched-Chain Fatty Acids in Plasma by Liquid Chromatography-Tandem Mass Spectrometry

Peroxisomal disorders are a heterogeneous group of genetic disorders caused by impaired peroxisomal biogenesis or by defects in single peroxisomal proteins. The most common peroxisomal disorders are Zellweger spectrum disorders (ZSDs), due to pathogenic variants in one of the 13 PEX genes, and X-linked adrenoleukodystrophy/adrenomyeloneuropathy (X-ALD/AMN), due to pathogenic variants in ATP-binding cassette transporter type D1 (ABCD1) gene. Peroxisomes perform multiple essential cellular functions, including β-oxidation of very-long-chain fatty acids (VLCFAs), pristanic acid and some bile acid intermediates, and α-oxidation of phytanic acid. In most patients, abnormal levels of VLCFAs and/or branched-chain fatty acids (BCFAs, e.g., phytanic and pristanic acids) are present; hence, measuring these analytes is critical when suspecting a peroxisomal disorder. This chapter describes a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantify VLCFAs and BCFAs in plasma or serum for the diagnosis of peroxisomal disorders. The method consists of an acid hydrolysis step to release the fatty acids from their coenzyme A esters followed by derivatization using oxalyl chloride, dimethylaminoethanol, and then methyl iodide. The trimethyl-amino-ethyl (TMAE) iodide ester derivatives are analyzed using UPLC-MS/MS in positive electrospray ionization and multiple reaction-monitoring (MRM) mode. Quantitation is performed using a five-point calibration curve after normalizing with deuterated internal standards.

The Effect of One Anastomosis Gastric Bypass on Branched-Chain Fatty Acid and Branched-Chain Amino Acid Metabolism in Subjects with Morbid Obesity

BACKGROUND

Subjects with morbid obesity have low levels of serum branched-chain fatty acids (BCFAs), which correlate inversely with insulin resistance, hypertriglyceridemia, and inflammation. Recent evidence suggests BCFAs are produced during branched-chain amino acid (BCAA) catabolism in human adipose tissue. Elevated concentrations of BCAAs are associated with insulin resistance.

OBJECTIVES

In this single-center study, we evaluated the effect of one anastomosis gastric bypass (OAGB) on circulating BCFA and BCAA. Moreover, we determined the expression of genes involved in BCAA catabolism in adipose tissue of patients with obesity and lean controls.

METHODS

Fasting levels of BCFAs and BCAAs were determined by gas and liquid chromatography, respectively, coupled with mass spectrometry, in 50 patients with morbid obesity before and 6-9 months after surgery, and in 32 lean controls. Visceral and subcutaneous adipose tissue (VAT and SAT, respectively) biopsies were collected at baseline to determine mRNA levels for enzymes involved in BCAA catabolism.

RESULTS

Before surgery, patients with obesity had lower BCFAs and greater BCAAs than control subjects. OAGB increased BCFA and decreased BCAA levels. Insulin resistance (assessed by HOMA) correlated inversely with BCFAs and positively with BCAAs. Expression of genes involved in BCAA catabolism in VAT (but not SAT) was lower in patients with obesity than in lean controls.

CONCLUSIONS

OAGB-induced weight loss increases circulating BCFAs and decreases circulating BCAAs in patients with morbid obesity, perhaps by altering BCAA catabolism in VAT. We speculate that this shift may be related to the improvement in insulin sensitivity after surgery.

Identification of novel small-molecule inhibitors of α-methylacyl-CoA racemase (AMACR; P504S) and structure-activity relationships

α-Methylacyl-CoA racemase (AMACR; P504S; EC 5.1.99.4) catalyses epimerization of 2-methylacyl-CoAs and is important for the degradation of branched-chain fatty acids and the pharmacological activation of ibuprofen and related drugs. It is also a novel drug target for prostate and other cancers. However, development of AMACR as a drug target has been hampered by the difficulties in assaying enzyme activity. Consequently, reported inhibitors have been rationally designed acyl-CoA esters, which are delivered as their carboxylate prodrugs. The novel colorimetric assay for AMACR based on the elimination of 2,4-dinitrophenolate was developed for high-throughput screening and 20,387 'drug-like compounds' were screened, with a throughput of 768 compounds assayed per day. Pyrazoloquinolines and pyrazolopyrimidines were identified as novel scaffolds and investigated as AMACR inhibitors. The most potent inhibitors have IC₅₀ values of ~2 µM. The pyrazoloquinoline inhibitor 10a displayed uncompetitive inhibition, whilst 10j displayed mixed competitive inhibition. The pyrazolopyrimidine inhibitor 11k displayed uncompetitive inhibition. This is the first report of the identification of specific drug-like small-molecule AMACR inhibitors by high-throughput screening. Pyrazoloquinolines and pyrazolopyrimidines may also be useful as inhibitors of other CoA-utilizing enzymes.

Branched-chain amino acid catabolism of Thermoanaerobacter strain AK85 and the influence of culture conditions on branched-chain alcohol formation

The bioprocessing of amino acids to branched-chain fatty acids and alcohols is described using Thermoanaerobacter strain AK85. The amino acid utilization profile was evaluated without an electron scavenger, with thiosulfate, and in a co-culture with a methanogen. There was an emphasis on the production of branched-chain alcohols and fatty acids from the branched-chain amino acids, particularly the influence of culture conditions which was investigated using isoleucine, which revealed that the concentration of thiosulfate was of great importance for the branched-chain alcohols/fatty acid ratio produced. Kinetic studies show that branched-chain amino acid fermentation is relatively slow as compared to glucose metabolism with the concentrations of the branched-chain alcohol increasing over time. To understand the flow of electrons and to investigate if the branched-chain fatty acid was being converted to branched-chain alcohol, enzyme assays and fermentation studies using ¹³C-labeled leucine and 3-methyl-1-butyrate were performed which indeed suggest that carboxylic acid reduction is a source of branched-chain alcohols when Thermoanaerobacter strain AK85 was cultivated with thiosulfate as an electron scavenger.

Structural basis of branched-chain fatty acid synthesis by Propionibacterium acnes β-ketoacyl acyl Carrier protein synthase

Propionibacterium acnes is an anaerobic gram-positive bacterium found in the niche of the sebaceous glands in the human skin, and is a causal pathogen of inflammatory skin diseases as well as periprosthetic joint infection. To gain effective control of P. acnes, a deeper understanding of the cellular metabolism mechanism involved in its ability to reside in this unique environment is needed. P. acnes exhibits typical cell membrane features of gram-positive bacteria, such as control of membrane fluidity by branched-chain fatty acids (BCFAs). Branching at the iso- or anteiso-position is achieved by incorporation of isobutyryl- or 2-methyl-butyryl-CoA via β-ketoacyl acyl carrier protein synthase (KAS III) from fatty acid synthesis. Here, we determined the crystal structure of P. acnes KAS III (PaKAS III) at the resolution of 1.9 Å for the first time. Conformation-sensitive urea polyacrylamide gel electrophoresis and tryptophan fluorescence quenching experiments confirmed that PaKAS III prefers isobutyryl-CoA as the acetyl-CoA, and the unique shape of the active site cavity complies with incorporation of branched-short chain CoAs. The determined structure clearly illustrates how BCFA synthesis is achieved in P. acnes. Moreover, the unique shape of the cavity required for the branched-chain primer can be invaluable in designing novel inhibitors of PaKAS III and developing new specifically targeted antibiotics.

NS12IITR for production of lipids with enriched branched-chain fatty acids for improving biodiesel properties along with hydrocarbon co-production

Hypersaline environment is inhabited by array of microbes which have the potential to produce industrially important products. This study explored biomass and lipid production potential of the halophilic bacterium, strain NS12IITR which was isolated from Sambhar Lake, Rajasthan. Sequencing and phylogenetic analysis revealed that the bacterium belonged to genus Lentibacillus. The salient feature of the isolate is its ability to accumulate total cellular lipid up to 18.9 ± 0.45% of dry cell weight. In addition, trans-esterification of extracted lipid yielded 77.6 ± 5.56% of total esters as methyl ester of branched-chain fatty acids (BCFAs). To assess the nature of extracted lipid, lipid sample was fractionated on the silicic acid column, which demonstrated that 49.03 ± 1.35% of the total lipids was neutral in nature. Trans-esterification of the neutral lipid fraction yielded 60.62 ± 4.88% of total esters as methyl ester of BCFAs. Methyl esters of BCFAs were present in trans-esterified products of neutral as well as polar lipid fractions. Furthermore, the isolate produced hydrocarbons both extracellularly (C₁₀-C₃₀) and intra-cellularly (C₁₅-C₂₈). The concentration of extracellular hydrocarbon (21.11 ± 0.78 mg/L) synthesized by strain NS12IITR is in close agreement with the yield reported from other hydrocarbon producing bacteria. This is hereby a first report on the co-production of lipids and hydrocarbon from a halophilic bacterium. The production of neutral lipid with high percentage of BCFAs and co-production of hydrocarbons makes the isolate NS12IITR a potential claimant for biofuel production.

A novel 1-acyl-sn-glycerol-3-phosphate O-acyltransferase homolog for the synthesis of membrane phospholipids with a branched-chain fatty acyl group in Shewanella livingstonensis Ac10

1-Acyl-sn-glycerol-3-phosphate O-acyltransferase (PlsC) plays an essential role in the formation of phosphatidic acid, a precursor of various membrane phospholipids (PLs), in bacteria by catalyzing the introduction of an acyl group into the sn-2 position of lysophosphatidic acid. Various bacteria produce more than one PlsC. However, the physiological significance of the occurrence of multiple PlsCs is poorly understood. A psychrotrophic bacterium, Shewanella livingstonensis Ac10, which produces eicosapentaenoic acid at low temperatures, has five putative PlsCs (PlsC1-5). We previously showed that PlsC1 is responsible for the production of PLs containing an eicosapentaenoyl group. Here, we characterized another putative PlsC of this bacterium named PlsC4. We generated a plsC4-disrupted mutant and found that PLs containing 13:0 found in the parental strain were almost completely absent in the mutant. The loss of these PLs was suppressed by introduction of a plsC4-expression plasmid. PLs containing 15:0 were also drastically decreased by plsC4 disruption. Gas chromatography-mass spectrometry analysis of fatty acyl methyl esters derived from PLs of the parental strain showed that the 13:0 and 15:0 groups were an 11-methyllauroyl group and a 13-methylmyristoyl group, respectively. Phospholipase A2 treatment revealed that these fatty acyl groups were linked to the sn-2 position of PLs. Thus, PlsC4 is a new type of PlsC homolog that is responsible for the synthesis of PLs containing a branched-chain fatty acyl group at the sn-2 position and plays a clearly different role from that of PlsC1 in vivo.

A novel case of ACOX2 deficiency leads to recognition of a third human peroxisomal acyl-CoA oxidase

Peroxisomal acyl-CoA oxidases catalyze the first step of beta-oxidation of a variety of substrates broken down in the peroxisome. These include the CoA-esters of very long-chain fatty acids, branched-chain fatty acids and the C27-bile acid intermediates. In rat, three peroxisomal acyl-CoA oxidases with different substrate specificities are known, whereas in humans it is believed that only two peroxisomal acyl-CoA oxidases are expressed under normal circumstances. Only three patients with ACOX2 deficiency, including two siblings, have been identified so far, showing accumulation of the C27-bile acid intermediates. Here, we performed biochemical studies in material from a novel ACOX2-deficient patient with increased levels of C27-bile acids in plasma, a complete loss of ACOX2 protein expression on immunoblot, but normal pristanic acid oxidation activity in fibroblasts. Since pristanoyl-CoA is presumed to be handled by ACOX2 specifically, these findings prompted us to re-investigate the expression of the human peroxisomal acyl-CoA oxidases. We report for the first time expression of ACOX3 in normal human tissues at the mRNA and protein level. Substrate specificity studies were done for ACOX1, 2 and 3 which revealed that ACOX1 is responsible for the oxidation of straight-chain fatty acids with different chain lengths, ACOX2 is the only human acyl-CoA oxidase involved in bile acid biosynthesis, and both ACOX2 and ACOX3 are involved in the degradation of the branched-chain fatty acids. Our studies provide new insights both into ACOX2 deficiency and into the role of the different acyl-CoA oxidases in peroxisomal metabolism.

Sex-dependent impact of Scp-2/Scp-x gene ablation on hepatic phytol metabolism

While prior studies focusing on male mice suggest a role for sterol carrier protein-2/sterol carrier protein-x (SCP-2/SCP-x; DKO) on hepatic phytol metabolism, its role in females is unresolved. This issue was addressed using female and male wild-type (WT) and DKO mice fed a phytoestrogen-free diet without or with 0.5% phytol. GC/MS showed that hepatic: i) phytol was absent and its branched-chain fatty acid (BCFA) metabolites were barely detectable in WT control-fed mice; ii) accumulation of phytol as well as its peroxisomal metabolite BCFAs (phytanic acid » pristanic and 2,3-pristenic acids) was increased by dietary phytol in WT females, but only slightly in WT males; iii) accumulation of phytol and BCFA was further increased by DKO in phytol-fed females, but much more markedly in males. Livers of phytol-fed WT female mice as well as phytol-fed DKO female and male mice also accumulated increased proportion of saturated straight-chain fatty acids (LCFA) at the expense of unsaturated LCFA. Liver phytol accumulation was not due to increased SCP-2 binding/transport of phytol since SCP-2 bound phytanic acid, but not its precursor phytol. Thus, the loss of Scp-2/Scp-x contributed to a sex-dependent hepatic accumulation of dietary phytol and BCFA.

High-Throughput Quantitative Lipidomics Analysis of Nonesterified Fatty Acids in Plasma by LC-MS

Nonesterified fatty acids are important biological molecules which have multiple functions such as energy storage, gene regulation, or cell signaling. Comprehensive profiling of nonesterified fatty acids in biofluids can facilitate studying and understanding their roles in biological systems. For these reasons, we have developed and validated a high-throughput, nontargeted lipidomics method coupling liquid chromatography to high-resolution mass spectrometry for quantitative analysis of nonesterified fatty acids. Sufficient chromatographic separation is achieved to separate positional isomers such as polyunsaturated and branched-chain species and quantify a wide range of nonesterified fatty acids in human plasma samples. However, this method is not limited only to these fatty acid species and offers the possibility to perform untargeted screening of additional nonesterified fatty acid species.

Modular pathway engineering for the microbial production of branched-chain fatty alcohols

The intrinsic structural properties of branched long-chain fatty alcohols (BLFLs) in the range of C12 to C18 make them more suitable as diesel fuel replacements and for other industrial applications than their straight-chain counterparts. While microbial production of straight long-chain fatty alcohols has been achieved, biosynthesis of BLFLs has never been reported. In this work, we engineered four different biosynthetic pathways in Escherichia coli to produce BLFLs. We then employed a modular engineering approach to optimize the supply of α-keto acid precursors and produced either odd-chain or even-chain BLFLs with high selectivity, reaching 70 and 75% of total fatty alcohols, respectively. The acyl-ACP and alcohol-producing modules were also extensively optimized to balance enzyme expression level and ratio, resulting in a 6.5-fold improvement in BLFL titers. The best performing strain overexpressed 14 genes from 6 engineered operons and produced 350 mg/L of BLFLs in fed-batch fermenter. The modular engineering strategy successfully facilitated microbial production of BLFLs and allowed us to quickly optimize new BLFL pathway with high titers and product specificity. More generally, this work provides pathways and knowledge for the production of BLFLs and BLFL-related, industry-relevant chemicals in high titers and yields.

An assessment of the fatty acid composition of horse-meat available at the retail level in northern Spain

The objective of the present study was to assess the fatty acid composition of horse-meat available at the retail market in northern Spain. Horse steaks (Longissimus thoracis et lumborum muscle; n=82) were purchased from butcher-shops and large grocery stores throughout six northern regions of Spain in two different seasons. Fat content differed significantly among regions (1.12 to 2.77%). Samples with higher intramuscular fat content presented the highest percentages of total monounsaturated fatty acids and the lowest contents of dimethylacetal and polyunsaturated fatty acids (PUFA), while the opposite was found in the leanest samples. A high variability was observed in the muscle and subcutaneous n-3 PUFA content. Overall, total n-3 PUFA content ranged between 1.17% and 18.9% in muscle fat and between 1.52% and 27.9% in backfat. Interestingly, almost 5% of surveyed loins from horse carcasses (4 out of 82) contained over 300mg of linolenic acid per 100g of meat which could have been marketed as a "source" of n-3 FAs according to Commission Regulation (EU) No 116/2010.

Broad substrate specificity of phosphotransbutyrylase from Listeria monocytogenes: A potential participant in an alternative pathway for provision of acyl CoA precursors for fatty acid biosynthesis

Listeria monocytogenes, the causative organism of the serious food-borne disease listeriosis, has a membrane abundant in branched-chain fatty acids (BCFAs). BCFAs are normally biosynthesized from branched-chain amino acids via the activity of branched chain α-keto acid dehydrogenase (Bkd), and disruption of this pathway results in reduced BCFA content in the membrane. Short branched-chain carboxylic acids (BCCAs) added as media supplements result in incorporation of BCFAs arising from the supplemented BCCAs in the membrane of L. monocytogenes bkd mutant MOR401. High concentrations of the supplements also effect similar changes in the membrane of the wild type organism with intact bkd. Such carboxylic acids clearly act as fatty acid precursors, and there must be an alternative pathway resulting in the formation of their CoA thioester derivatives. Candidates for this are the enzymes phosphotransbutyrylase (Ptb) and butyrate kinase (Buk), the products of the first two genes of the bkd operon. Ptb from L. monocytogenes exhibited broad substrate specificity, a strong preference for branched-chain substrates, a lack of activity with acetyl CoA and hexanoyl CoA, and strict chain length preference (C3-C5). Ptb catalysis involved ternary complex formation. Additionally, Ptb could utilize unnatural branched-chain substrates such as 2-ethylbutyryl CoA, albeit with lower efficiency, consistent with a potential involvement of this enzyme in the conversion of the carboxylic acid additives into CoA primers for BCFA biosynthesis.

Short branched-chain C6 carboxylic acids result in increased growth, novel 'unnatural' fatty acids and increased membrane fluidity in a Listeria monocytogenes branched-chain fatty acid-deficient mutant

Listeria monocytogenes is a psychrotolerant food borne pathogen, responsible for the high fatality disease listeriosis, and expensive food product recalls. Branched-chain fatty acids (BCFAs) of the membrane play a critical role in providing appropriate membrane fluidity and optimum membrane biophysics. The fatty acid composition of a BCFA-deficient mutant is characterized by high amounts of straight-chain fatty acids and even-numbered iso fatty acids, in contrast to the parent strain where odd-numbered anteiso fatty acids predominate. The presence of 2-methylbutyrate (C5) stimulated growth of the mutant at 37°C and restored growth at 10°C along with the content of odd-numbered anteiso fatty acids. The C6 branched-chain carboxylic acids 2-ethylbutyrate and 2-methylpentanoate also stimulated growth to a similar extent as 2-methylbutyrate. However, 3-methylpentanoate was ineffective in rescuing growth. 2-Ethylbutyrate and 2-methylpentanoate led to novel major fatty acids in the lipid profile of the membrane that were identified as 12-ethyltetradecanoic acid and 12-methylpentadecanoic acid respectively. Membrane anisotropy studies indicated that growth of strain MOR401 in the presence of these precursors increased its membrane fluidity to levels of the wild type. Cells supplemented with 2-methylpentanoate or 2-ethylbutyrate at 10°C shortened the chain length of novel fatty acids, thus showing homeoviscous adaptation. These experiments use the mutant as a tool to modulate the membrane fatty acid compositions through synthetic precursor supplementation, and show how existing enzymes in L. monocytogenes adapt to exhibit non-native activity yielding unique 'unnatural' fatty acid molecules, which nevertheless possess the correct biophysical properties for proper membrane function in the BCFA-deficient mutant.

Hydrolysis of ibuprofenoyl-CoA and other 2-APA-CoA esters by human acyl-CoA thioesterases-1 and -2 and their possible role in the chiral inversion of profens

Ibuprofen and related 2-arylpropanoic acid (2-APA) drugs are often given as a racemic mixture and the R-enantiomers undergo activation in vivo by metabolic chiral inversion. The chiral inversion pathway consists of conversion of the drug to the coenzyme A ester (by an acyl-CoA synthetase) followed by chiral inversion by α-methylacyl-CoA racemase (AMACR; P504S). The enzymes responsible for hydrolysis of the product S-2-APA-CoA ester to the active S-2-APA drug have not been identified. In this study, conversion of a variety of 2-APA-CoA esters by human acyl-CoA thioesterase-1 and -2 (ACOT-1 and -2) was investigated. Human recombinant ACOT-1 and -2 (ACOT-1 and -2) were both able to efficiently hydrolyse a variety of 2-APA-CoA substrates. Studies with the model substrates R- and S-2-methylmyristoyl-CoA showed that both enzymes were able to efficiently hydrolyse both of the epimeric substrates with (2R)- and (2S)- methyl groups. ACOT-1 is located in the cytosol and is able to hydrolyse 2-APA-CoA esters exported from the mitochondria and peroxisomes for inhibition of cyclo-oxygenase-1 and -2 in the endoplasmic reticulum. It is a prime candidate to be the enzyme responsible for the pharmacological action of chiral inverted drugs. ACOT-2 activity may be important in 2-APA toxicity effects and for the regulation of mitochondrial free coenzyme A levels. These results support the idea that 2-APA drugs undergo chiral inversion via a common pathway.