Degradation of long chain alkanes by bacilli

Summary Among 14 different types of bacillus and 100 isolates from soil samples, no bacillus was able to assimilate C₁₄-C₁₈ alkanes as sole carbon source. In contrast to these results, five types of bacillus were substantially able to oxidize alkanes in the presence of other carbon sources.All five strains tested formed relatively high amounts of secondary alcohol in contrast to low amounts of ketones and traces of primary alcohols with chain length equivalent to the n-alkane in the substrate, showing that the degradation pathway in bacilli is mainly subterminal.This conclusion is also supported by comparison of the extracellular fatty acids of cultures of bacilli grown on n-tridecane and on n-tetradecane supplemented with other carbon sources and on the same carbon sources without alkane.     

Degradation of long chain alkanes by bacilli

Summary Degradation of tetradecane by two thermophilic Bacillus strains was investigated. It was found that these strains do not grow on this hydrocarbon as sole carbon source but degrade tetradecane in cooxidation cultures partly via monoterminal pathway.     

Degradation of long chain n-alkanes by Mucorales

Summary The degradation pathways on n-dodecane and n-tridecane were studied in seven representative strains of five families of the order Mucorales. Using thin-layer chromatographic, gas-liquid chromatographic and mass spectrometric methods, extracellular oxidation products of the relevant n-alkanes could be isolated and identified. All strains tested exhibited a formation of isomeric primary and secondary alcohols, isomeric ketones and monoic acids with chain length equivalent to the n-alkanes in the substrates, proving that in the order Mucorales both a terminal and a subterminal oxidation pathway are realized.     

Degradation of long chain n-alkanes by Chlorococcales

Summary Four out of thirty-one algae strains belonging to the order Chlorococcales exhibited good growth on solid media containing n-alkanes. Chlorella vulgaris (397) was able to degrade n-tridecane in cooxidation. The corresponding secondary alcohols and ketones in C₂-to C₇-position could be identified in the culture broth. The same oxidation products could be found in the media of cultures grown in darkness with the addition of glucose. This demonstrates a subterminal degradation pathway of C. vulgaris.There was no indication for a mono-or diterminal oxidation of alkanes by algae.The fatty acid pattern of lipids exhibited an incease in long chain acids and a decrease in shorter chain acids. The growth rate of cells grown on alkanes increased after 72 h, but the release of autospores was retarded.     

Degradation of long chain n-alkanes by mucorales

Summary Extracellular oxidation products isolated from the substrates ofMortierella isabellina (CBS 224. 35) grown on n-dodecane and n-tridecane were primary and secondary isomeric alcohols, isomeric ketones, aldehydes and isomeric esters with the same numbers of carbon atoms presented in the used n-alkanes as detected by combined glass capillary gas chromatography — mass spectrometry. All esters were identified which theoretically could originate in the isomeric ketones by a reaction mechanism resembling a Baeyer-Villinger-type oxidation.     

Degradation of alkanes by bacteria

Pollution of soil and water environments by crude oil has been, and is still today, an important problem. Crude oil is a complex mixture of thousands of compounds. Among them, alkanes constitute the major fraction. Alkanes are saturated hydrocarbons of different sizes and structures. Although they are chemically very inert, most of them can be efficiently degraded by several microorganisms. This review summarizes current knowledge on how microorganisms degrade alkanes, focusing on the biochemical pathways used and on how the expression of pathway genes is regulated and integrated within cell physiology.     

Degradation of long chain n-alkanes by disrupted cells ofChlorella vulgaris

Summary The alkane oxidation byChlorella vulgaris is improved by disruption of the cells. Although living cells are not able to attack n-dodecane, disrupted cells produced detectable amounts of oxidation products. The amount of isomeric alcohols and ketones of n-tridecane was nearly double the sum found in living cells, whereas the equilibrium was shifted to the ketones. With n-tetradecane and n-pentadecane only the amount of ketones increased.     

Monte Carlo simulation of branched alkanes and long chain n -alkanes with anisotropic united atoms intermolecular potential

The anisotropic united atoms potential for linear alkanes proposed by Ungerer (J. Chem. Phys. , 112 , 5499, 2000), called AUA4, has been used to predict several equilibrium properties (vapour pressure, vaporisation enthalpies, and liquid densities) of alkanes by Gibbs ensemble Monte Carlo simulation. In order to extend the potential to branched alkanes, potential parameters for the CH group have been determined by optimisation on the basis of equilibrium properties of isobutane, keeping the same parameters as AUA4 for the CH 3 groups. The resulting CH parameters form a regular sequence with those previously determined for CH 3 and CH 2 groups, so that a physically consistent parameter set is obtained. Simulations have been performed at temperatures ranging from 450 to 800 u K for long n -alkanes (C20, C25 and C30) and from 350 to 450 u K for four heptane isomers (n -heptane, 2-methylhexane, 2,4-dimethylpentane and 2-ethylpentane). In order to achieve internal relaxation of long chains with a good efficiency, a specific Monte Carlo move was used in which a united atom is rotated around its nearest neighbours. Equilibrium properties of long chain alkanes are well predicted, and small differences between heptane isomers are represented with a good accuracy. It is concluded that the AUA4 potential shows an interesting degree of transferability.     

Degradation of very long chain dicarboxylic polyunsaturated fatty acids in mouse hepatocytes, a peroxisomal process

Polyunsaturated fatty acids can be omega-oxidized to dicarboxylic polyunsaturated fatty acids (DC-PUFA), bioactive compounds which cause vasodilatation and activation of PPARalpha and gamma. DC-PUFA can be shortened by beta-oxidation, and to determine whether mitochondria and/or peroxisomes are responsible for this degradation 20-carboxy-[1-(14)C]-eicosatetraenoic acid (20-COOH-AA) was synthesized and given to hepatocytes from mouse models with peroxisomal dysfunctions. In contrast to wild type cells, hepatocytes from mice with liver-selective elimination of peroxisomes, due to Pex5p deficiency, failed to produce (14)CO(2) and labeled acid-soluble oxidation products, indicating that peroxisomes are involved in the degradation of 20-COOH-AA. Subsequently, the oxidation of 20-COOH-AA was analyzed in hepatocytes lacking multifunctional protein 1 (MFP1) or MFP2, key enzymes of the peroxisomal beta-oxidation. Degradation of 20-COOH-AA was partially impaired in MFP1, but not in MFP2 knockout hepatocytes. Taken together, peroxisomes and not mitochondria are the site of beta-oxidation of DC-PUFA, and MFP1 is involved in this process.     

Platelet aggregation is inhibited by long chain acyl-CoA

Oleoyl coenzyme A and other acyl-CoA derivatives inhibited ADP or thrombin-induced aggregation of platelets. Arachidonic acid-induced aggregation was also inhibited, but not the slower aggregation caused by 1-oleoyl-2-acetylglycerol or tetradecanoyl-phorbol-13-acetate. Coenzyme A and free fatty acids had little or no effect, and transfer of labeled oleate from oleoyl Co-A to other lipid classes was not detected. Because acyl Co-A compounds have recently been shown to modulate protein kinase C activity, acyl Co-A may provide a useful tool for investigating activation sequences in platelets and other membranes.     

Degradation pathways of cyclic alkanes in Rhodococcus sp. NDKK48

The degradation pathways for cyclic alkanes (c-alkanes) in Rhodococcus sp. NDKK48 were investigated. Strain NDKK48 used dodecylcyclohexane as a sole carbon and energy source, and five metabolites in the dodecylcyclohexane degradation pathway were detected by gas-chromatography/mass spectra. The metabolites were identified as cyclohexanecarboxylic acid, cyclohexylacetic acid, 1-cyclohexene-1-acetic acid, 4-dodecylcyclohexanol, and 4-dodecylcyclohexanone. The strain degrades dodecylcyclohexane via a ring oxidation pathway and an alkyl side chain oxidation pathway. Cyclohexanecarboxylic acid was further oxidized to muconic acid via 1-cyclohexene-1-carboxylic acid and benzoic acid, and the muconic acid was finally used by strain NDKK48 for growth. Methylcyclohexane and cyclohexane were co-oxidized with hexadecane by strain NDKK48. Methylcyclohexane was degraded via a ring oxidation pathway, and the degradation pathway contained part of the Baeyer-Villiger oxidation for ring cleavage. Cyclohexane was also degraded by the same pathway as methylcyclohexane. Thus, strain NDKK48 has two pathways for the complete degradation of c-alkanes.     

Inhibition of chymase activity by long chain fatty acids

The activity of chymase was markedly inhibited by fatty acids with carbon chain lengths of 14-22 at doses greater than 0.02 microM, irrespective of the number of double bonds. Cis acids with a carbon chain length of 18, such as stearic acid, oleic acid, linoleic acid, and linolenic acid were potent inhibitors, whereas the trans isomer of oleic acid, elaidic acid, showed less inhibitory activity. The extent of inhibition by oleyl alcohol was almost the same as that by oleic acid, suggesting that the acid moiety itself was not necessary for the inhibition; but a fatty acid with a terminal functional amide, oleamide, showed little inhibitory activity. The inhibition was noncompetitive and was reversible, and the Ki value of oleic acid was 2.7 microM. Stearic acid and oleic acid inhibited all chymotrypsin-type serine endopeptidases tested. The ID50 values of these fatty acids for atypical mast cell protease were higher than those for the other chymotrypsin-type serine endopeptidases tested. Other proteases, such as papain, trypsin, collagenase, and carboxypeptidase A, except cathespin D, were not affected by stearic or oleic acid.     

Deficiency of very long chain alkanes biosynthesis causes humidity‐sensitive male sterility via affecting pollen adhesion and hydration in rice

Pollen adhesion and hydration are the earliest events of the pollen–stigma interactions, which allow compatible pollen to fertilize egg cells, but the underlying mechanisms are still poorly understood. Rice pollen are wind dispersed, and its pollen coat contains less abundant lipids than that of insect‐pollinated plants. Here, we characterized the role of OsGL1‐4, a rice member of the Glossy family, in pollen adhesion and hydration. OsGL1‐4 is preferentially expressed in pollen and tapetal cells and is required for the synthesis of very long chain alkanes. osgl1‐4 mutant generated apparently normal pollen but displayed excessively fast dehydration at anthesis and defective adhesion and hydration under normal condition, but the defective adhesion and hydration were rescued by high humidity. Gas chromatography–mass spectrometry analysis suggested that the humidity‐sensitive male sterility of osgl1‐4 was probably due to a significant reduction in C25 and C27 alkanes. These results indicate that very long chain alkanes are components of rice pollen coat and control male fertility via affecting pollen adhesion and hydration in response to environmental humidity. Moreover, we proposed that a critical point of water content in mature pollen is required for the initiation of pollen adhesion.     

Lipolysis of natural long chain and synthetic medium chain galactolipids by pancreatic lipase-related protein 2

Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) are the most abundant lipids in nature, mainly as important components of plant leaves and chloroplast membranes. Pancreatic lipase-related protein 2 (PLRP2) was previously found to express galactolipase activity, and it is assumed to be the main enzyme involved in the digestion of these common vegetable lipids in the gastrointestinal tract. Most of the previous in vitro studies were however performed with medium chain synthetic galactolipids as substrates. It was shown here that recombinant guinea pig (Cavia porcellus) as well as human PLRP2 hydrolyzed at high rates natural DGDG and MGDG extracted from spinach leaves. Their specific activities were estimated by combining the pH-stat technique, thin layer chromatography coupled to scanning densitometry and gas chromatography. The optimum assay conditions for hydrolysis of these natural long chain galactolipids were investigated and the optimum bile salt to substrate ratio was found to be different from that established with synthetic medium chains MGDG and DGDG. Nevertheless the length of acyl chains and the nature of the galactosyl polar head of the galactolipid did not have major effects on the specific activities of PLRP2, which were found to be very high on both medium chain [1786 ± 100 to 5420 ± 85 U/mg] and long chain [1756 ± 208 to 4167 ± 167 U/mg] galactolipids. Fatty acid composition analysis of natural MGDG, DGDG and their lipolysis products revealed that PLRP2 only hydrolyzed one ester bond at the sn-1 position of galactolipids. PLRP2 might be used to produce lipid and free fatty acid fractions enriched in either 16:3 n − 3 or 18:3 n − 3 fatty acids, both found at high levels in galactolipids.