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At least 19 recordsLinked to original sources

PubMed1975

Hydrophobic interaction of alkanes with liposomes and lipoproteins.

Human serum lipoproteins and egg yolk lecithin liposomes are able to solubilize large amounts of n-hexane and n-octane. At the maximum water solubility of n-octane the mole ratio of alkane to lipoprotein was 65 for high density lipoprotein (holo-HDL) and 900 for low density lipoprotein (holo-LDL). Alkane binding to lipid-free apo-HDL is negligible compared to alkane solubility in holo-HDL. Alkane solubility in the lipoproteins and liposomes is thermodynamically consistent with the simple soution of hydrocarbon in the hydrophobic regions of these particles. The unitary free energies of alkane transfer are similar to values previously observed for detergent micelles but are less favorable by 0.8 kcal/mol from the free energy of transfer to liquid hydrocarbon. It is concluded that the thermodynamics of alkane transfer to the lipoproteins resembles that found for detergent micelles or liposomes rather than that anticipated for an "oil drop" (i.e. liquid hydrocarbon).

Alkanes↗

PubMedDate not supplied

[n-Alkane oxidation by propionic acid bacteria].

Propionic acid bacteria were found for the first time to be capable of oxidizing n-alkanes. The value of QO2 is higher on a mixture of n-alkanes (C12--C20) than on individual hydrocarbons whose availability is determined by the length of a hydrocarbon chain: C15 and C16-alkanes are oxidized best of all; C14, C13 and C12-alkanes are oxidized at a lower rate; and alkanes whose chain comprises less than ten carbon atoms are not oxidized at all. Hexadecane is oxidized to CO2, cetyl alcohol and palmitic acid being intermediates; this suggests the existence of the monoterminal pathway for oxidation of n-alkanes in propionic acid bacteria.

Alkanes↗

PubMed2026

Viral communities from long-term anaerobic alkane-oxidizing enrichment cultures encode predicted cell surface adhesion functions.

The anaerobic oxidation of methane and C2+-alkanes is a dominant metabolism within hydrocarbon-rich deep-sea sediments and is largely mediated by alkane-oxidizing archaea in metabolic partnership with syntrophic sulfate-reducing bacteria. Although these processes fuel a diverse ecosystem, the viral component of alkane-rich sediments has historically been overlooked. We analyzed the viral assemblages in long-term sediment-free cultures of alkane-degrading organisms and found that abiotic factors such as incubation temperature had a greater correlation with community composition than with the phylogenetic patterns among individual viral species. No auxiliary metabolic genes (AMGs) directly involved in hydrocarbon oxidation or sulfate reduction were found, but the presence of candidate AMGs involved in heme synthesis pathways common in methane oxidizers hints at a possible viral impact on alkane degradation. We also examined potential host-virus pairs using CRISPR- and tRNA-based methods. Lastly, we identified the presence of nosD-like proteins in viruses from sediment-derived systems that are not present in water column datasets; their distribution, genomic context, and lack of canonical nosD characteristics suggest an alternate adhesion-related role in sediment communities. The number of new viruses obtained from these multi-year enrichment cultures and their potential roles in mediating host physiology illustrate the importance of studying the viral component in laboratory and environmental systems.

Geologic Sediments↗

PubMed1977

Fractionation of inducible alkane hydroxylase activity in Pseudomonas putida and characterization of hydroxylase-negative plasmid mutations.

The plasmid-determined inducible alkane hydroxylase of Pseudomonas putida resolved into particulate and soluble fractions. Spinach reductase and spinach ferredoxin could replace the soluble hydroxylase component. Two alkane hydroxylase mutants show in vitro complementation (S. Benson and J. Shapiro, J. Bacteriol., 123: 759-760, 1975): one, alk-7, lacks an active soluble component and the other, alk-181, lacks an active particulate component. Together with previous results on a particulate alcohol dehydrogenase enzyme (Benson and Shapiro, J. Bacteriol., 126: 794-798, 1976), these results allowed us to assay three plasmid-determined inducible activities: soluble alkane hydroxylase (alkA+), particulate alkane hydroxylase (alkB+), and particulate alcohol dehydrogenase (alkC+). Growth tests and in vitro complementation assays revealed three groups of plasmid mutations that block expression of alkane hydroxylase activity: alkA, which so far includes only the alk-7 mutation; alkB, which includes alk-181 and 11 other mutations; and a pleiotropic-negative class, which includes nine mutations that lead to loss of alkA+, alkB+, and alkC+ activities. Thus, the alk+ gene cluster found on IncP-2 plasmids contains at least four cistrons. We believe it is significant that two of these determined the presence of membrane proteins. The accompanying paper shows that these loci are part of a single regulon.

Alkanes↗

PubMed1977

Production of uricase by Candida tropicalis using n-alkane as a substrate.

Production of uricase (urate oxidase, EC 1.7.3.3) by n-alkane-utilizing Candida tropicalis pK233 was studied. Although the yeast showed very low enzyme productivity under growing conditions on glucose or an n-alkane mixture (C10 to C13) (less than 2 U/g of dry cells), enzyme formation was enhanced markedly in an induction medium consisting of potassium phosphate buffer, MgSO4, uric acid, and an n-alkane mixture (47 U/g of dry cells) or glucose (21 U/g of dry cells). Of the carbon sources tested, the n-alkane mixture was the most suitable for enzyme production. Appropriate aeration also stimulated uricase formation. In addition to uric acid, xanthine, guanine, adenine, and hypoxanthine were also effective for inducing uricase. Under optimum conditions, the maximum yield of the enzyme was 91 U/g of dry cells. Uricase thus induced was localized in the microbodies of the yeast.

Alkanes↗

PubMed1977

Isolation, crystallization, and properties of indolyl-3-alkane alpha-hydroxylase. A novel tryptophan-metabolizing enzyme.

Indolyl-3-alkane alpha-hydroxylase, a novel tryptophan-metabolizing enzyme, was prepared in crystalline form from soil isolate organism Pseudomonas XA. Emission spectroscopy and atomic absorption analyses of purified enzyme revealed the presence of iron (0.8 mol/mol of protein), and a number of observations supported the presence of heme prosthetic group (1.1 mol/mol of protein). The S20,w value of indolyl-3-alkane alpha-hydroxylase is 10.2 S, and the molecular weight by sedimentation equilibrium ultracentrifugation is 250,000. The E1%280 of the enzyme is 21, and the isoelectric point by isoelectric focusing on ampholine polyacrylamide gel plates is 4.8. The enzyme catalyzes hydroxylation on the side chain of a variety of 3-substituted indole compounds, including certain tryptophan-containing oligopeptides. The reaction product from tryptamine was identified by proton nuclear magnetic resonance and gas chromatography/mass spectroscopy analyses. While the indole ring remained intact, hydroxylation occurred at the side chain carbon adjacent to the ring. Nuclear magnetic resonance studies indicated that hydroxylation always took place at the same position when the substrate was tryptophan methyl ester, tryptophol, indole-3-propionate, or indole-3-butyrate. No other chemical change occurred when these substrates were incubated with the enzyme. The Km value of indolyl-3-alkane alpha-hydroxylase for L-tryptophan is 2.4 X 10(-6) M, at pH 7.2. The enzyme is inhibited by potassium cyanide (0.1 mM) or hydroxylamine (1mM), but not by NaBH4 (25 mM), aminooxyacetic acid (7mM), quinacrine (1 mM), chlortetracycline (1 mM), p-mercuribenzoate (0.1 mM), or ethylenediaminetetraacetate (1 mM). The plasma half-life (t1/2) of indolyl-3-alkane alpha-hydroxylase in tumor-bearing mice is approximately 25 h.

Amino Acids↗

PubMed1975

An analysis of intermediary metabolism and its control in a fat-synthesizing yeast (Candida 107) growing on glucose or alkanes.

Enzymes of glycolysis, pentose phosphate pathway, gluconeogenesis, tricarboxylate acid cycle, glyoxylate by-pass and fatty-acid biosynthesis were assayed in extracts from Candida 107 grown continuously on glucose under carbon limitation, nitrogen limitation and on n-alkanes. The yeast was therefore either in a lipogenic or lipolytic state. Phosphofructokinase was absent under all conditions whereas enzymes of gluconeogenesis, including fructose 1,6-bisphosphatase and the pentose phosphate cycle, were all present. Glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were specific for NADP+ and were inhibited in a non-competitive manner by NADPH and NADH. Phosphoenolpyruvate, citrate, ATP and acetyl CoA had no inhibitory effects. Thus glucose metabolism appears to be by the pentose phosphate pathway which will rapidly produce NADPH. This can readily be consumed during fatty-acid biosynthesis and, as there appears to be no inhibition of the flow of carbon from glucose to acetyl CoA, fatty-acid synthesis can continue for as long as there is a supply of glucose. These results help to explain the probable causes of fat build-up to high concentrations (about 40% of the cell dry weight) in this and other organisms. In alkane-grown cells, lipogenesis is repressed and carbon is able to flow from the alkanes via acetyl CoA, oxaloacetate and pyruvate into pentoses and hexoses in a unidirectional manner, because of the strong repression of pyruvate kinase and the increased activities of phosphoenolpyruvate kinase and fructose 1,6-biosphosphatase under these conditions. Although there was little change in the total activity of the TCA cycle enzymes under the various growth conditions, isocitrate lyase was induced under lipolytic conditions.

Acetyl Coenzyme A↗

PubMedDate not supplied

[Electrophoretic differences in the proteins of the species Pseudomonas aeruginosa and Pseudomonas denitrificans capable of oxidizing n-alkanes].

Pseudomonas aeruginosa and Ps. denitrificans are capable of growing on n-alkanes, but differ in assimilation of higher and lower alkanes. The proteins of their cell-free homogenates were analysed by disc-electrophoresis in a system containing SDS. The "preliminarily adapted" strain of Ps. aeruginosa did not differ from the "non-adapted" to n-hexane strain, though both differed considerably from Ps. denitrificans in the composition of protein spectrum. Therefore, disc-electrophoresis of total proteins has shown that Ps. aeruginosa and Ps. denitrificans are not genetically identical; they exhibit certain common physiological properties, but apparently oxidize n-alkanes via different pathways.

Alkanes↗

PubMed1979

The alkane-hydroxylating enzyme system of the yeast Candida guilliermondii.

The growth of the investigated Candida guilliermondii strain on n-alkanes induces an alkane-hydroxylating enzyme system, which consists of a cytochrome P-450 and a NADPH-dependent reductase. The cytochrome P-450 was purified to 4 nmoles per mg protein. Long-chain alkanes, preferably hexadecane to octadecane, are hydroxylated to the corresponding primary alcohol by this enzyme system. The substrate induces a type I spectrum, other compounds checked type II spectra.

Alkanes↗

PubMed1977

Stimulatory effect of n-alkanes on CTP: Cholinephosphate cytidyltransferase activity in rat liver microsomal membranes in vitro.

To assess the effect of alteration of membrane structure on the enzymic activities related to phospholipid synthesis in microsomal membrane, the effects of several organic solvents have been studied in an in vitro system, in which the cytoplasmic extract prepared from rat liver incorporated [14C]choline or [14C]CDP-choline into phosphatidycholine (lecithin). The optimum conditions for the incorporation were determined. Among several organic solvents examined, n-alkanes such as n-hexane, n-octane, and n-tetradecane stimulated the incorporation. It was shown that n-alkanes stimulated one of three enzymic steps of lecithin biosynthesis from choline; that is, the formulation of CDP-choline catalyzed by CTP: cholinephosphate cytidyltransferase [EC 2.7.7.15], an enzyme on the microsomal membrane. It was further shown that the same enzyme was also stimulated by preincubation of microsomes in the absence of substrate. It is suggested that alteration of the lipid environment of the microsomal membrane induced by n-alkanes caused activation of this enzymic step.

Alkanes↗

PubMed1978

Cytochrome P-450 and alkane hydroxylase activity in Candida guilliermondii.

In the investigated Candida guilliermondii strain after growth on n-alkanes as the only carbon and energy source 5--10 nMol cytochrome P-450 per g cells (wet weight) could be detected. Cytochrome P-450 and alkane hydroxylase activity was found in the 100 000 xg pellet. Cofactor studies and inhibition experiments revealed the existence of a NADPH-dependent cytochrome P-450 alkane hydroxylase system.

Alkanes↗

PubMed1978

The blockage of the electrical conductance in a pore-containing membrane by the n-alkanes.

1. In monooelein bilayers made highly conducting by the addition of a fixed amount of o-pyromellitylgramicidin, the membrane conductance has been shown to be strongly dependent on the chain length of the n-alkane with which the membrane is in equilibrium. Thus for n-hexadecane, the conductance is larger by approx. 10(4) times than it is for n-octane. This result is independent of whether the polypeptide is introduced via the aqueous or lipid phases. 2. The observed conductance variations have been accounted for in terms of a mechanism (outlined in earlier publications) which is based on the thickness and tension changes produced in bilayers by the adsorption of n-alkanes. Essentially quantitative agreement between theory and experiment is found.

Alkanes↗

PubMed1977

The soluble methane mono-oxygenase of Methylococcus capsulatus (Bath). Its ability to oxygenate n-alkanes, n-alkenes, ethers, and alicyclic, aromatic and heterocyclic compounds.

1. Methane mono-oxygenase of Methylococcus capsulatus (Bath) catalyses the oxidation of various substituted methane derivatives including methanol. 2. It is a very non-specific oxygenase and, in some of its catalytic properties, apparently resembles the analogous enzyme from Methylomonas methanica but differs from those found in Methylosinus trichosporium and Methylomonas albus. 3. CO is oxidized to CO2. 4. C1-C8 n-alkanes are hydroxylated, yielding mixtures of the corresponding 1- and 2-alcohols; no 3- or 4-alcohols are formed. 5. Terminal alkenes yield the corresponding 1,2-epoxides. cis- or trans-but-2-ene are each oxidized to a mixture of 2,3-epoxybutane and but-2-en-1-ol with retention of the cis or trans configuration in both products; 2-butanone is also formed from cis-but-2-ene only. 6. Dimethyl ether is oxidized. Diethyl ether undergoes sub-terminal oxidation, yielding ethanol and ethanal in equimolar amounts. 7. Methane mono-oxygenase also hydroxylates cyclic alkanes and aromatic compounds. However, styrene yields only styrene epoxide and pyridine yields only pyridine N-oxide. 8. Of those compounds tested, only NADPH can replace NADH as electron donor.

Alkanes↗

PubMed1975

Extracellular lipids of Cladosporium (Amorphotheca) resinae grown on glucose or on n-alkanes.

Cladosporium (Amorphotheca) resinae was grown in shake culture on glucose, n-dodecane, or n-hexadecane. Growth was most rapid on glucose, and more acid accumulated in the medium than in n-alkane-grown cultures. Neutral lipid was the major lipid fraction and triglycerides were the only extracellular neutral lipids detected. Dodecanoic (lauir) acid was the predominant fatty acid (greater than 60%) in neutral lipids from all three media, with lesser amounts of tetradecanoic, hexadecanoic, and octadecanoic acids. Extracellular phospholipids identified were phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and cardiolipin or a cardiolipin-like compound. Phospholipids from all three media contained dodecanoic acid as their principle fatty acid. Dodecanoic acid was the only extracellular free fatty acid detected. Glucose medium contained acetic, glyoxylic, and glycolic acids and an unidentified organic acid which may contribute to the lower pH in cultures after growth on glucose. In all classes of extracellular lipids the fatty acids do not correspond to the fatty acids previously determined to be associated with cellular lipids. Moreover, the fatty acids of extracellular lipids do not reflect the chain length of the n-alkane growth substrate.

Acetates↗

PubMed1976

Plasmid-determined alcohol dehydrogenase activity in alkane-utilizing strains of Pseudomonas putida.

We have identified an alcohol dehydrogenase activity in Pseudomonas putida strains carrying the CAM-OCT degradative plasmid that were grown on octane. The activity is nicotinamide adenine dinucleotide independent, sediments at 48,000 x g, and shows 20-fold greater activity with octanol rather than butanol as substrate. The enzyme is inducible by unoxidized alkane and is present only in strains that have the OCT plasmid genes for alkane degradation with a wild-type alcO locus. No analogous chromosomal dehydrogenase could be detected. Wild-type and actanol-negative mutants (alcA-) without plasmids both contain a constitutive nicotinamide adenine dinucleotide-linked soluble alcohol dehydrogenase activity. This means that alcA- mutants are cryptic for octanol oxidation and suggests that the particulate plasmid-coded alcohol dehydrogenase activity is active on surface- or membrane-bound substrate.

Alcohol Oxidoreductases↗

PubMed1979

[Lipids of Candida lipolytica cultivated in n-alkanes by the industrial method ("Toprina")].

The following lipidic classes are examined in the present study: Total Lipids, Phospholipids, Neutral Lipids, Sterols, and Carotenoid Pigments from dried biomasses of Candida lipolytica grown on n-alkanes by industrial process following the BP technique ("Toprina"). The composition of the lipid classes examined in "Toprina" agree generally with bibliographic data about n-alkanes grown Candida lipolytica in batch cultures.

Alkanes↗

PubMedDate not supplied

Metabolism of chlorinated alkenes and alkanes as related to toxicity.

The chlorine substitution in aliphatic compounds results, by its electron attracting effect, in a destabilization in alkanes and a stabilization in alkenes. Thus, with alkanes the main pathways of metabolic transformation to reactive intermediates are radical formation by C-C break or dechlorination, or dehydrochlorination. In alkenes, the stability of the molecule increases with the number of chlorine substitutions. In the series of chlorinated ethylenes, the first step of metabolic transformation is the oxidation to electrophilic oxiranes which may be hydrolized enzymatically or non-enzymatically, react with cellular nucleophiles, or rearrange to either chlorinated aldehydes or acyl chlorides. With tetra-, 1,2-cis- and trans-di-, 1,1-di-, and monochloroethylene, the metabolites identified in in vivo experiments are identical with the thermal rearrangement products of the respective oxiranes. An important exception is found with trichloroethylene, where the thermal rearrangement product is dichloroacetyl chloride; the metabolites in vivo, however, are entirely derived from trichloroacetaldehyde (chloral). The reason for this peculiar behavior is most probably a Lewis acid catalysis by the oxidizing enzyme system. Mutagenic and carcinogenic activities in the series of chlorinated ethylenes are determined by the stability of their oxiranes, which is higher in symmetrical than in unsymmetrical chlorine substitution: the relatively unstable and unsymmetric oxiranes of trichloroethylene, 1, 1,-dichloro-, and monochloroethylene are mutagenic in the Ames test; the more stable symmetric oxiranes of tetra-, 1,2-cis- and trans-dichloroethylenes are inactive.

Animals↗

PubMed1975

The behaviour of NAD+ and NADH in Acinetobacter calcoaceticus during n-alkane assimilation.

The behaviour of the nicotinamide adenine dinucleotides NAD+ and NADH in Acinetobacter calcoaceticus during n-alkane assimilation was studied, acetate and succinate being used as reference carbon sources. The intracellular concentration of the two nucleotides was found to increase during the exponential growth phase, reaching its maximum in the phase of decreasing growth rates. In the exponential phase, the NAD+/NADH quotients were less than 1 and showed only unimportant variations. In the phase of decreasing growth rates, the concentration of NADH showed a distinct decrease, reaching its minimum in the stationary phase. Parallel to this, the concentration of NAD+ showed a continuous increase until the stationary phase was reached. This resulted in an increase, during the phase of decreasing growth rates, of the NAD+/NADH quotients to values greater than 1, similarly as recorded in the stationary phase. There were no fundamental differences in this behaviour between the individual carbon sources.

Acetates↗