Analysis of the acyl-CoAs that accumulate during the peroxisomal beta-oxidation of arachidonic acid and 6,9,12-octadecatrienoic acid

Compositional Analysis of Non-Polar and Polar Metabolites in 14 Soybeans Using Spectroscopy and Chromatography Tools

There has been significant interest in soybean oil, fatty acid, and sugar composition to develop new value-added soybean products. Thus, compositional analysis is critical for developing value-added soybeans. In the present study, we showed simple screening tools (near infrared spectroscopy (NIR) and high-performance thin layer chromatography (HPTLC)) coupled with multivariate analysis for the sample classification of 14 soybeans as a proof-of-concept. We further determined major non-polar and polar metabolites responsible for differences between different soybeans using gas and ion chromatography. These differences in soybean profiles were attributed to lower levels of total oil content in wild soybeans (~9%) versus cultivated soybeans (16%–22%). In addition, higher levels of linolenic acid (~17%) and stachyose (~53%) were determined in wild type, whereas higher levels of oleic acid (~19%) and sucrose (~59%) were detected in cultivated soybeans. Interestingly, one cultivated soybean had a desirable sugar profile with a high amount of sucrose (86%) and a low abundance of stachyose (9%). The correlation studies showed a positive correlation between oil and soluble sugars (R² = 0.80) and negative correlations between methyl linolenate and soluble sugars (R² = −0.79), oil (R² = −0.94), and methyl oleate (R² = −0.94) content. Both polar and non-polar metabolites showed significant differences in wild and cultivated soybeans.

Genomic changes and biochemical alterations of seed protein and oil content in a subset of fast neutron induced soybean mutants

BACKGROUND

Soybean is subjected to genetic manipulation by breeding, mutation, and transgenic approaches to produce value-added quality traits. Among those genetic approaches, mutagenesis through fast neutrons radiation is intriguing because it yields a variety of mutations, including single/multiple gene deletions and/or duplications. Characterizing the seed composition of the fast neutron mutants and its relationship with gene mutation is useful towards understanding oil and protein traits in soybean.

RESULTS

From a large population of fast neutron mutagenized plants, we selected ten mutants based on a screening of total oil and protein content using near infra-red spectroscopy. These ten mutants were regrown, and the seeds were analyzed for oil by GC-MS, protein profiling by SDS-PAGE and gene mapping by comparative genomic hybridization. The mutant 2R29C14Cladecr233cMN15 (nicknamed in this study as L10) showed higher protein and lower oil content compared to the wild type, followed by three other lines (nicknamed in this study as L03, L05, and L06). We characterized the fatty acid methyl esters profile of the trans-esterified oil and found the presence of five major fatty acids (palmitic, stearic, oleic, linoleic, and linolenic acids) at varying proportions among the mutants. Protein profile using SDS-PAGE of the ten mutants did exhibit discernable variation between storage (glycinin and β-conglycinin) and anti-nutritional factor (trypsin inhibitor) proteins. In addition, we physically mapped the position of the gene deletions or duplications in each mutant using comparative genomic hybridization.

CONCLUSION

Characterization of oil and protein profile in soybean fast neutron mutants will assist scientist and breeders to develop new value-added soybeans with improved protein and oil quality traits.

Quantitative Proteomic Analysis of Low Linolenic Acid Transgenic Soybean Reveals Perturbations of Fatty Acid Metabolic Pathways

To understand the effect of fatty acid desaturase gene (GmFAD3) silencing on perturbation of fatty acid (FA) metabolic pathways, the changes are compared in protein profiling in control and low linolenic acid transgenic soybeans using tandem mass tag based mass spectrometry. Protein profiling of the transgenic line unveiled changes in several key enzymes of FA metabolism. This includes enzymes of lower abundance; fabH, fabF, and thioestrase associated with FA initiation, elongation, and desaturation processes and LOX1_5, ACOX, ACAA1, MFP2 associated with β-oxidation of α-linolenic acids pathways. In addition, the GmFAD3 silencing results in a significant reduction in one of the major allergens, Gly m 4 (C6T3L5). These results are important for exploring how plants adjust in their biological processes when certain changes are induced in the genetic makeup. A complete understanding of these processes will aid researchers to alter genes for developing value-added soybeans.

Dietary effects of arachidonate-rich fungal oil and fish oil on murine hepatic and hippocampal gene expression

BACKGROUND

The functions, actions, and regulation of tissue metabolism affected by the consumption of long chain polyunsaturated fatty acids (LC-PUFA) from fish oil and other sources remain poorly understood; particularly how LC-PUFAs affect transcription of genes involved in regulating metabolism. In the present work, mice were fed diets containing fish oil rich in eicosapentaenoic acid and docosahexaenoic acid, fungal oil rich in arachidonic acid, or the combination of both. Liver and hippocampus tissue were then analyzed through a combined gene expression- and lipid- profiling strategy in order to annotate the molecular functions and targets of dietary LC-PUFA.

RESULTS

Using microarray technology, 329 and 356 dietary regulated transcripts were identified in the liver and hippocampus, respectively. All genes selected as differentially expressed were grouped by expression patterns through a combined k-means/hierarchical clustering approach, and annotated using gene ontology classifications. In the liver, groups of genes were linked to the transcription factors PPARalpha, HNFalpha, and SREBP-1; transcription factors known to control lipid metabolism. The pattern of differentially regulated genes, further supported with quantitative lipid profiling, suggested that the experimental diets increased hepatic beta-oxidation and gluconeogenesis while decreasing fatty acid synthesis. Lastly, novel hippocampal gene changes were identified.

CONCLUSIONS

Examining the broad transcriptional effects of LC-PUFAs confirmed previously identified PUFA-mediated gene expression changes and identified novel gene targets. Gene expression profiling displayed a complex and diverse gene pattern underlying the biological response to dietary LC-PUFAs. The results of the studied dietary changes highlighted broad-spectrum effects on the major eukaryotic lipid metabolism transcription factors. Further focused studies, stemming from such transcriptomic data, will need to dissect the transcription factor signaling pathways to fully explain how fish oils and arachidonic acid achieve their specific effects on health.

Alternatives to the isomerase-dependent pathway for the beta-oxidation of oleic acid are dispensable in Saccharomyces cerevisiae. Identification of YOR180c/DCI1 encoding peroxisomal delta(3,5)-delta(2,4)-dienoyl-CoA isomerase

Fatty acids with double bonds at odd-numbered positions such as oleic acid can enter beta-oxidation via a pathway relying solely on the auxiliary enzyme Delta(3)-Delta(2)-enoyl-CoA isomerase, termed the isomerase-dependent pathway. Two novel alternative pathways have recently been postulated to exist in mammals, and these additionally depend on Delta(3,5)-Delta(2,4)-dienoyl-CoA isomerase (di-isomerase-dependent) or on Delta(3,5)-Delta(2,4)-dienoyl-CoA isomerase and 2,4-dienoyl-CoA reductase (reductase-dependent). We report the identification of the Saccharomyces cerevisiae oleic acid-inducible DCI1 (YOR180c) gene encoding peroxisomal di-isomerase. Enzyme assays conducted on soluble extracts derived from yeast cells overproducing Dci1p using 3,5,8,11,14-eicosapentenoyl-CoA as substrate demonstrated a specific di-isomerase activity of 6 nmol x min(-1) per mg of protein. Similarly enriched extracts from eci1Delta cells lacking peroxisomal 3,2-isomerase additionally contained an intrinsic 3,2-isomerase activity that could generate 3, 5,8,11,14-eicosapentenoyl-CoA from 2,5,8,11,14-eicosapentenoyl-CoA but not metabolize trans-3-hexenoyl-CoA. Amplification of this intrinsic activity replaced Eci1p since it restored growth of the eci1Delta strain on petroselinic acid for which di-isomerase is not required whereas Eci1p is. Heterologous expression in yeast of rat di-isomerase resulted in a peroxisomal protein that was enzymatically active but did not re-establish growth of the eci1Delta mutant on oleic acid. A strain devoid of Dci1p grew on oleic acid to wild-type levels, whereas one lacking both Eci1p and Dci1p grew as poorly as the eci1Delta mutant. Hence, we reasoned that yeast di-isomerase does not additionally represent a physiological 3,2-isomerase and that Dci1p and the postulated alternative pathways in which it is entrained are dispensable for degrading oleic acid.

Regulation of the biosynthesis of 22:5n-6 and 22:6n-3: a complex intracellular process

Both 22:4n-6 and 22:5n-3 are synthesized from n-6 and n-3 fatty acid precursors in the endoplasmic reticulum. The synthesis of both 22:5n-6 and 22:6n-3 requires that 22:4n-6 and 22:5n-3 are metabolized, respectively, to 24:5n-6 and 24:6n-3 in the endoplasmic reticulum. These two 24-carbon acids must then move to peroxisomes for partial degradation followed by the movement of 22:5n-6 and 22:6n-3 back to the endoplasmic reticulum for use as substrates in membrane lipid biosynthesis. Clearly an understanding of the control of intracellular fatty acid movement as well as of the reactions carried out by microsomes, peroxisomes, and mitochondria are all required in order to understand not only what regulates the biosynthesis of 22:5n-6 and 22:6n-3 but also why most tissue lipids selectively accumulate 22:6n-3.

Polyunsaturated fatty acid biosynthesis: a microsomal-peroxisomal process

The synthesis of 22-carbon fatty acids, with their first double bond at position 4, requires the participation of enzymes in both peroxisomes and the endoplasmic reticulum as well as the controlled movement of fatty acids between these two cellular compartments. It has been observed that there is generally an inverse relationship between rates of peroxisomal beta-oxidation vs those for the microsomal esterification of fatty acids into 1-acyl-sn-glycero-3-phosphocholine. With a variety of different substrates it was found that when a fatty acid is produced in peroxisomes, with its first double bond at position 4, its preferred metabolic fate is to move to microsomes for esterification rather than to serve as a substrate for continued degradation. The required movement, and the associated reactions, in peroxisomes and microsomes is not restricted to the synthesis of 4,7,10,13,16-docosapentaenoic acid and 4,7,10,13,16,19-docosahexaenoic acid. When microsomes and peroxisomes were incubated with NAD, NADPH and malonyl-CoA it was found that 6,9,12-octadecatrienoic acid was metabolized to linoleate. Collectively our findings suggest that there may be considerably more recycling of fatty acids between peroxisomes and the endoplasmic reticulum than was previously recognized.

A comparison of the metabolism of [3-14C]-labeled 22- and 24-carbon (n-3) and (n-6) unsaturated fatty acids by rat testes and liver

The unsaturated fatty acid composition of phospholipids from different tissues frequently varies. Rat liver phospholipids contain esterified 22:6(n-3) while 22:5(n-6) is the major esterified 22-carbon acid in testes phospholipids. Both testes and liver synthesize polyunsaturated fatty acids. Microsomes, particularly from liver, have been used extensively to measure reaction rates as they relate to polyunsaturated fatty acid and phospholipid biosynthesis. None of these rate studies explain why specific acids are synthesized and subsequently esterified. In this study we compared the metabolism of [3-14C]-labeled (n-3) and (n-6) acids when injected via the tail vein, as a measure of hepatic metabolism, versus when they were injected directly into the testes. Liver preferentially metabolizes [3-14C]-labeled 24:5(n-3) and 24:6(n-3) to yield esterified 22:6(n-3), when compared with the conversion of [3-14C]-labeled 24:4(n-6) and 24:5(n-6) to yield 22:5(n-6). Both 24-carbon (n-3) acids were also converted to 22:5(n-3) but no labeled 22:4(n-6) was detected after injecting the two 24-carbon (n-6) acids. Differences in the hepatic metabolism of 24-carbon (n-3) and (n-6) acids to 22:6(n-3) and 22:5(n-6), versus their partial beta-oxidation to 22:5(n-3) and 22:4(n-6), are important in vivo controls. Surprisingly, in testes a higher percentage of radioactivity was found in esterified 22:6(n-3) versus 22:5(n-6) following injections, respectively, of [3-14C]-labeled 22:5(n-3) versus 22:4(n-6), which is the corresponding metabolic analog. Corresponding pairs of 24-carbon (n-3) and (n-6) acids, as they relate to metabolism, were processed in similar ways by testes. The relative absence of esterified 22-carbon (n-3) fatty acids, versus the abundance of 22- and 24-carbon (n-6) acids in testes phospholipids, does not appear per se to be due to differences in the ability of testes to metabolize (n-3) and (n-6) fatty acids. It remains to be determined if there is selective uptake of specific fatty acids by testes for use as precursors to synthesize polyunsaturated fatty acids.

An update on the pathways of polyunsaturated fatty acid metabolism

The biosynthesis of 4, 7, 10, 13, 16-22:5 and 4, 7, 10, 13, 16, 19-22:6 from dietary linoleate and linolenate, respectively, does not totally take place in the endoplasmic reticulum but does require the participation of enzymes in the endoplasmic reticulum and peroxisomes. The absence of an endoplasmic reticulum-associated acyl-CoA-dependent delta 4 desaturase also requires the controlled movement of 22- and 24-carbon polyunsaturated fatty acids between the endoplasmic reticulum and peroxisomes.