The synthesis of fatty acids in avocado mesocarp and cauliflower bud tissue.
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ABSTRACT:
SUBMITTER: Weaire PJ
PROVIDER: S-EPMC1165321 | biostudies-other | 1975 Feb
REPOSITORIES: biostudies-other
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Project description:1. An avocado supernatant fraction converted fatty acids of medium chain length (C(8)-C(12)) into a polar product. 2. The product was identified as the beta-hydroxy derivative of the substrate by g.l.c. and t.l.c. analysis. 3. For hydroxylation of the fatty acids, CoA, ATP and molecular oxygen were required. Acyl carrier protein gave some stimulation. The reaction took place with oxygen alone if acyl-CoA was the substrate. 4. Hydroxylation was maximal with decanoic acid but dodecanoic acid and octanoic acid were also very active. Acids of shorter or longer chain lengths were not hydroxylated. 5. NAD(+) concentration caused complete inhibition at 0.5mm and may be an important control mechanism for the reaction in vivo. 6. The reaction was inhibited by iodoacetamide and by bipyridyl and carbon monoxide, indicating involvement of thiol and heavy metal groups.
| S-EPMC1174551 | biostudies-other
Project description:1. The range of fatty acids formed by preparations of ultrasonically ruptured avocado mesocarp plastids was dependent on the substrate. Whereas [1-14C]palmitate and [14C]oleate were the major products obtained from [-14C]acetate and [1-14C]acetyl-CoA, the principal product from [2-14C]malonyl-CoA was [14-C]stearate. 2. Ultracentrifugation of the ruptured plastids at 105000g gave a supernatant that formed mainly stearate from [2-14C]malonyl-CoA and to a lesser extent from [1-14C]acetate. The incorporation of [1-14C]acetate into stearate by this fraction was inhibited by avidin. 3. The 105000g precipitate of the disrupted plastids incorporated [1-14C]acetate into a mixture of fatty acids that contained largely [14C]plamitate and [14C]oleate. The formation of [14C]palmitate and [14C]oleate by disrupted plastids was unaffected by avidin. 4. The soluble fatty acid synthetase was precipitated from the 105000g supernatant in the 35-65%-saturated-(NH4)2SO4 fraction and showed an absolute requirement for acyl-carrier protein. 5. Both fractions synthesized fatty acids de novo.
| S-EPMC1165322 | biostudies-other
Project description:Chilling injury (CI) symptoms in avocado (Persea americana Mill.) fruit, expressed as mesocarp discoloration, were found to be associated with embryo growth and ethylene production during cold storage. In cvs Ettinger and Arad most mesocarp discoloration was located close to the base of the seed and was induced by ethylene treatment in seeded avocado fruit. However, ethylene did not increase mesocarp discoloration in seedless fruit stored at 5 degrees C. Application of ethylene to whole fruit induced embryo development inside the seed. It also induced seedling elongation when seeds were imbibed separately. Persea americana ethylene receptor (PaETR) gene expression and polyphenol oxidase activity were highest close to the base of the seed and decreased gradually toward the blossom end. By contrast, expressions of PaETR transcript and polyphenol oxidase activity in seedless avocado fruit were similar throughout the pulp at the base of the fruit. Application of the ethylene inhibitor, 1-methylcyclopropene, decreased mesocarp browning, embryo development, seedling growth, and ion leakage, and down-regulated polyphenol oxidase activity. The results demonstrate that ethylene-mediated embryo growth in whole fruit is involved in the mesocarp response to ethylene perception and the development of CI disorders.
| S-EPMC2652053 | biostudies-literature
Project description:The NADPH-linked 3-oxoacyl-(acyl-carrier protein) (ACP) reductase (EC 1.1.1.100), also known as 'beta-ketoacyl-ACP reductase', has been purified from the mesocarp of mature avocado pears (Persea americana). The enzyme is inactivated by low ionic strength and low temperature. On SDS/PAGE under reducing conditions, purified 3-oxoacyl-ACP reductase migrated as a single polypeptide giving a molecular mass of 28 kDa. Gel-filtration chromatography gave an apparent native molecular mass of 130 kDa, suggesting that the enzyme is tetrameric. The enzyme is inactivated by dilution, but some protection is afforded by the presence of NADPH. Kinetic constants have been determined using synthetic analogues as well as the natural ACP substrate. It exhibits a broad pH optimum around neutrality. Phenylglyoxal inactivates the enzyme, and partial protection is given by 1 mM-NADPH. Antibodies have been raised against the protein, which were used to localize it using immunogold electron microscopy. It is localized in plastids. N-Terminal amino-acid-sequence analysis was performed on the enzyme, and it shows close structural similarity with cytochrome f. Internal amino-acid-sequence data, derived from tryptic peptides, shows similarity with the putative gene products encoded by the nodG gene from the nitrogen-fixing bacterium Rhizobium meliloti and the gra III act III genes from Streptomyces spp.
| S-EPMC1149621 | biostudies-other
Project description:BackgroundAvocado fruit contains aliphatic acetogenins (oft-acetylated, odd-chain fatty alcohols) with promising bioactivities for both medical and food industries. However, we have scarce knowledge about their metabolism. The present work aimed to study changes in acetogenin profiles from mesocarp, lipid-containing idioblasts, and seeds from 'Hass' cultivar during fruit development, germination, and three harvesting years. An untargeted LC-MS based lipidomic analysis was also conducted to profile the lipidome of avocado fruit in each tissue.ResultsThe targeted analysis showed that acetogenin profiles and contents remained unchanged in avocado mesocarp during maturation and postharvest ripening, germination, and different harvesting years. However, a shift in the acetogenin profile distribution, accompanied with a sharp increase in concentration, was observed in seed during early maturation. Untargeted lipidomics showed that this shift was accompanied with remodeling of glycerolipids: TAGs and DAGs decreased during fruit growing in seed. Remarkably, the majority of the lipidome in mature seed was composed by acetogenins; we suggest that this tissue is able to synthesize them independently from mesocarp. On the other hand, lipid-containing idioblasts accumulated almost the entire acetogenin pool measured in the whole mesocarp, while only having 4% of the total fatty acids. The lipidome of this cell type changed the most when the fruit was ripening after harvesting, TAGs decreased while odd-chain DAGs increased. Notably, idioblast lipidome was more diverse than that from mesocarp.ConclusionsEvidence shown here suggests that idioblasts are the main site of acetogenin biosynthesis in avocado mesocarp. This work unveiled the prevalence of aliphatic acetogenins in the avocado fruit lipidome and evidenced TAGs as initial donors of the acetogenin backbones in its biosynthesis. It also sets evidence for acetogenins being included in future works aimed at characterizing the avocado seed, as they are a main component of their lipidome.
| S-EPMC5623960 | biostudies-literature
Project description:BackgroundAvocado (Persea americana) is an economically important tropical fruit considered to be a good source of fatty acids. Despite its importance, the molecular and cellular characterization of biochemical and developmental processes in avocado is limited due to the lack of transcriptome and genomic information.ResultsThe transcriptomes of seeds, roots, stems, leaves, aerial buds and flowers were determined using different sequencing platforms. Additionally, the transcriptomes of three different stages of fruit ripening (pre-climacteric, climacteric and post-climacteric) were also analyzed. The analysis of the RNAseqatlas presented here reveals strong differences in gene expression patterns between different organs, especially between root and flower, but also reveals similarities among the gene expression patterns in other organs, such as stem, leaves and aerial buds (vegetative organs) or seed and fruit (storage organs). Important regulators, functional categories, and differentially expressed genes involved in avocado fruit ripening were identified. Additionally, to demonstrate the utility of the avocado gene expression atlas, we investigated the expression patterns of genes implicated in fatty acid metabolism and fruit ripening.ConclusionsA description of transcriptomic changes occurring during fruit ripening was obtained in Mexican avocado, contributing to a dynamic view of the expression patterns of genes involved in fatty acid biosynthesis and the fruit ripening process.
| S-EPMC4533766 | biostudies-literature
Project description:1. A ;malic' enzyme [l-malate-NAD oxidoreductase (decarboxylating), EC 1.1.1.39] has been isolated from cauliflower bud mitochondria and partially purified. 2. The enzyme is specific for l-malate and has an absolute requirement for either Mn(2+), Co(2+) or Mg(2+). 3. The enzyme shows activity with both NAD(+) and NADP(+), but NAD(+) is the preferred cofactor. 4. No appreciable oxaloacetate decarboxylase activity is present in the enzyme preparations even at low pH values. 5. The enzyme is inhibited by NADH and by oxaloacetate and stimulated by SO(4) (2-) and by low concentrations of CoA. 6. The regulatory properties of the enzyme support the proposed role of the enzyme in the utilization of tricarboxylic acid-cycle acids for energy production when glycolysis is suppressed.
| S-EPMC1176806 | biostudies-other
Project description:Eukaryotes harbor a highly conserved mitochondrial pathway for fatty acid synthesis (FAS), which is completely independent of the eukaryotic cytosolic FAS apparatus. The activities of the mitochondrial FAS system are catalyzed by soluble enzymes, and the pathway thus resembles its prokaryotic counterparts. Except for octanoic acid, which is the direct precursor for lipoic acid synthesis, other end products and functions of the mitochondrial FAS pathway are still largely enigmatic. In addition to low cellular levels of lipoic acid, disruption of genes encoding mitochondrial FAS enzymes in yeast results in a respiratory-deficient phenotype and small rudimentary mitochondria. Recently, two distinct links between mitochondrial FAS and RNA processing have been discovered in vertebrates and yeast, respectively. In vertebrates, the mitochondrial 3-hydroxyacyl-acyl carrier protein dehydratase and the RPP14 subunit of RNase P are encoded by the same bicistronic transcript in an evolutionarily conserved arrangement that is unusual for eukaryotes. In yeast, defects in mitochondrial FAS result in inefficient RNase P cleavage in the organelle. The intersection of mitochondrial FAS and RNA metabolism in both systems provides a novel mechanism for the coordination of intermediary metabolism in eukaryotic cells.
| S-EPMC2666548 | biostudies-literature
Project description:Using isolated amyloplasts from cauliflower buds, we have characterized the interaction and transport of various carbohydrates across the envelope membrane of a heterotrophic plastid. According to our results, glucose 6-phosphate (Glc6P) and glucose 1-phosphate (Glc1P) do not share the same transport protein for uptake into cauliflower-bud amyloplasts. Glc6P-dependent starch synthesis is strongly inhibited in the presence of dihydroxyacetone phosphate (DHAP) or 4,4'-di-isothiocyano-2,2'- stilbenedisulphonic acid (DIDS), whereas Glc1P-dependent starch synthesis is hardly affected by these compounds. Analysis of the Glc6P uptake into proteoliposomes reconstituted from the envelope proteins of cauliflower-bud amyloplasts indicate that Glc6P is taken up in a counter-exchange mode with Pi, DHAP or Glc6P, whereas Glc1P does not act as a counter-exchange substrate. Pi is a strong competitive inhibitor of Glc6P uptake (Ki 0.8 mM) into proteoliposomes, whereas Glc1P does not significantly inhibit Glc6P transport. Beside a hexose-phosphate translocator, these amyloplasts possess an envelope protein mediating the transport of glucose across the membrane. This translocator exhibits an apparent Km for glucose of 2.2 mM and is inhibited by low concentrations of phloretin, known to be a specific inhibitor of glucose-transport proteins. Maltose inhibits the uptake of glucose (Ki 2.3 mM), indicating that both carbohydrates share the same translocator.
| S-EPMC1136679 | biostudies-other