Synthesis of RNA,Protein, Cellulose,and Mucopolysaccharide and Changes in the Chemical Composition of Hartmannella culbertsoni During Encystment under Axenic Conditions*

Hartmannella culbertsoni trophozoites are transformed into viable cysts on exposure to a non-nutrient agar medium containing 15 mM MgCl₂ and 20 mM taurine. Amebae differentiating in this encystment medium incorporate more uracil-2-¹⁴C into RNA and more leucine-1-¹⁴C or valine-1-¹⁴C into proteins than controls. Encysting organisms incorporate significantly more glucose-U-¹⁴C into cellulose and glucosamine-1-¹⁴C into mucopolysaccharides. Incorporation of glucose-U-¹⁴C into cellulose and of glucosamine-1-¹⁴C into mucopolysaccharides are inhibited by actinomycin D or cycloheximide.     

Studies on the biosynthesis of phenols in fungi. Production of 4-methoxytoluquinol, epoxysuccinic acid and a diacetylenic alcohol by surface cultures of Lentinus degener I.M.I. 110525

1. 4-Methoxytoluquinol was secreted into the medium by surface cultures of the basidiomycete Lentinus degener Kalchbr. (approx. 100mg./l. of medium). In addition, epoxysuccinic acid (150–200mg.) and a long-chain diacetylenic alcohol (3mg.) were also secreted. Epoxysuccinic acid has previously been found in the culture medium of some Fungi Imperfecti. These metabolites were all synthesized during the early phase of growth but maximum production occurred some time later. 2. Supplementation of the medium with cycloheximide or 8-azaguanine inhibited the production of epoxysuccinic acid. 3. Sodium [1-¹⁴C]acetate and 6-methyl[¹⁴C]salicylic acid were not incorporated into 4-methoxytoluquinol, but [U-¹⁴C]tyrosine and [Me-¹⁴C]methionine were incorporated to the extent of 0·55 and 4·75% respectively (minimum values). Degradation studies established that the aromatic ring and C-methyl group were derived from the ring and β-carbon atom of tyrosine; the O-methyl group alone was formed from methionine.     

Biosynthesis of lipids in chloroplasts isolated from jack pine needles

Suspensions of isolated pine needle chloroplasts were shown to incorporate galactose from UDP galactose-[¹⁴C] into galactolipids. The incorporation of the label among galactolipids was always considerably higher in the monogalactosyl diglycerides than in the digalactosyl diglycerides. The galactosyl incorporation into both galactolipid fractions was optimal at pH 8.0 and was inhibited by sulphydryl reagents (p-chloromercuribenzoate, N-ethyl maleimide and CdCl₂). The chloroplast preparations were also able to biosynthesize various phospholipids and galactolipids from palmitoyl-[1-¹⁴C]-CoA; the major portion of the label appeared in phosphatidyl choline. The incorporation of palmitic-[1-¹⁴C] acid into various lipids was very poor compared to that of palmitoyl-[1-¹⁴C]-CoA. However, addition of ATP and CoA markedly stimulated lipid biosynthesis from palmitic-[1-¹⁴C] acid, suggesting the presence of activating enzymes. These chloroplast suspensions did not show any de novo fatty acid synthesis.     

Compartmentation of citric acid cycle metabolism in brain: effect of aminooxyacetic acid, ouabain and Ca2+ on the labelling of glutamate, glutamine, aspartate and gaba by [1-14C]acetate, [U-14C]glutamate and [U-14C]asparate

—(1) The effects of aminooxyacetic acid, ouabain and Ca²⁺ on the compartmentation of amino acid metabolism have been studied in slices of brain incubated with sodium-[1-¹⁴C]acetate, l-[U-¹⁴C]glutamate and l-[U-¹⁴C]aspartate as tracer metabolites. (2) Aminooxyacetic acid (10^-3 m) inhibited the labelling of aspartate from [¹⁴C]acetate and [¹⁴C]glutamate, as well as the incorporation of label from [¹⁴C]aspartate into glutamate and glutamine. It also inhibited the labelling of GABA from all three radioactive precursors, as would be anticipated if there was inhibition of several transaminases as well as glutamate decarboxylase. The RSA of glutamine labelled from [1-¹⁴C]acetate was increased. This finding indicated that the glutamate pool which is utilized for glutamine formation is associated with glutamate dehydrogenase, and this enzyme appears to be related to the ‘synthetic tricarboxylic acid cycle’. AOAA exerted its major inhibitory effects on the citric acid‘energy cycle’with which transaminases are associated. (3) Ouabain (10^-5 m) inhibited the labelling of glutamine to a much greater extent than the labelling of glutamate from [1-¹⁴C]acetate. It also caused leakage of amino acids from the tissue into the medium. Its effect on the glutamate–glutamine system was interpreted to be a selective inhibition of the 'synthetic’citric acid cycle. (4) The omission of Ca²⁺ from the incubation medium was associated with formation of glutamine with RSA less than 1·0 when labelled from [U-¹⁴C]glutamate, [U-¹⁴C]aspartate and lower than normal when labelled from [1-¹⁴C]acetate.     

Arachidonate metabolism in bovine gallbladder muscle

Incubation of [1-¹⁴C]arachidonic acid (AA) with homogenates of bovine gallbladder muscle generated a large amount of radioactive material having the chromatographic mobility of 6-keto-PGF_1α (stable product of PGI₂) and smaller amounts of products that comigrated with PGF_2α and PGE₂. Formation of these products was inhibited by the cyclooxygenase inhibitor indomethacin. The major radioactive product identified by thin-layer chromatographic mobility and by gas chromatography - mass spectrometric analysis was found to be 6-keto-PGF_1α. The quantitative metabolic pattern of [1-¹⁴C]PGH₂ was virtually identical to that of [1-¹⁴C]AA. Incubation of arachidonic acid with slices of bovine gallbladder muscle released labile anti-aggregatory material in the medium, which was inhibited by aspirin or 15-hydroperoxy-AA.These results indicate that bovine gallbladder muscle has a considerable enzymatic capacity to produce PGI₂ from arachidonic acid.     

Translocation of cytidine 5′-monophosphosialic acid across golgi apparatus membranes

Golgi apparatus, isolated from rat liver, incorporate [¹⁴C]sialic acid from CMP[¹⁴C]sialic acid into endogenous glycolipid and glycoprotein acceptors. Incorporation of [¹⁴C]sialic acid into endogenous glycoprotein acceptors was stimulated an average of 3-fold by Triton X-100 at an optimal concentration of 0.05% and was inhibited at higher concentrations. Incorporation of [¹⁴C]sialic acid into endogenous glycolipid acceptors was not stimulated by detergent. The major glycolipid product was identified by thin-layer chromatography as the ganglioside G_d3. SDS-polyacrylamide gel electrophoresis of the glycoprotein products demonstrated incorporation of [¹⁴C]sialic acid into 6–7 major bands. Neuraminidase studies determined that approximately 60% of the [¹⁴C]sialic acid incorporated into endogenous acceptors in the absence of detergent had a luminal orientation. Furthermore, electron microscopy studies showed that the isolated Golgi apparatus fraction consisted of intact membrane cisternae. Our results demonstrate that sialylation of cisternal acceptors located on the inside of the membrane occurs in the absence of detergent. They are consistent with carrier-mediated transport as a mechanism to allow CMPsialic acid to traverse the Golgi apparatus membrane and to be used to glycosylate endogenous glycoprotein and glycolipid acceptors.     

Effect of 4-Pentenoic Acid on Intermediate Metabolism of Tetrahymena*

SYNOPSIS. The growth of Tetrahymena pyriformis strain HSM was strongly inhibited by 4-pentenoic acid. Supplementing the medium with acetate reversed the growth inhibition, but pyruvate was ineffective. Glycogen content was much lower in cells grown with 4-pentenoic acid than in controls; this effect was not reversed by acetate or by pyruvate. There was little effect of 4-pentenoic acid on the incorporation of label from [1-¹⁴C]acetate, [2-¹⁴C]glycerol, [1-³⁴]ribose, [U-¹⁴C]fructose, or [1-¹⁴C]glucose into CO₂, but incorporation of label into glycogen was inhibited, the strongest inhibition being on acetate and the weakest (～ 20%) on ribose, fructose, and glucose. A 3-compartment model for quantitation of labeled acetyl CoA fluxes was shown to be applicable to Tetrahymena grown in the presence of 4-pentenoic acid, and experiments were performed to establish the flux of [1-¹⁴C]acetyl CoA into glycogen, lipids, CO₂, glutamate, and alanine. It was evident from the results of these experiments that 4-pentenoic acid did not appreciably inhibit β-oxidation or lipogenesis, but markedly decreased the glyconeogenic flux of labeled acetyl-CoA from the peroxismal and outer mitochondrial compartments. At least 2 mechanisms have been proposed for the action of 4-pentenoic acid: (a) reduction of the levels of acetyl CoA or free CoA and (b) direct inhibition of enzymes by 4-pentenoyl CoA or its metabolites. Although 4-pentenoic acid has little effect on acetyl-CoA metabolism in the inner mitochondrial compartment, the present data suggest that the flux through the outer mitochondrial compartment of acetyl-CoA derived from pyruvate is inhibited largely by the first, and that the glyconeogenic flux of acetyl-CoA is inhibited largely by the 2nd mechanism.     

Studies on the regulation of leucine catabolism: Mechanism responsible for oxidizable substrate inhibition and dichloroacetate stimulation of leucine oxidation by the heart

In the absence of any other oxidizable substrate, the perfused rat heart oxidizes [1-¹⁴C]leucine to ¹⁴CO₂ at a rapid rate and releases only small amounts of α-[1-¹⁴C]ketoisocaproate into the perfusion medium. The branched-chain α-keto acid dehydrogenase complex, assayed in extracts of mitochondria prepared from such perfused hearts, is very active. Under such perfusion conditions, dichloroacetate has almost no effect on [1-¹⁴C]leucine oxidation, α-[1-¹⁴C]ketoisocaproate release, or branched-chain α-keto acid dehydrogenase activity. Perfusion of the heart with some other oxidizable substrate, e.g., glucose, pyruvate, ketone bodies, or palmitate, results in an inhibition of [1-¹⁴C]leucine oxidation to ¹⁴CO₂ and the release of large amounts of α-[1-¹⁴C]ketoisocaproate into the perfusion medium. The branched-chain α-keto acid dehydrogenase complex, assayed in extracts of mitochondria prepared from such hearts, is almost completely inactivated. The enzyme can be reactivated, however, by incubating the mitochondria at 30 °C without an oxidizable substrate. With hearts perfused with glucose or ketone bodies, dichloroacetate greatly increases [1-¹⁴C]leucine oxidation, decreases α-[1-¹⁴C]ketoisocaproate release into the perfusion medium, and activates the branched-chain α-keto acid dehydrogenase complex. Pyruvate may block dichloroacetate uptake because dichloroacetate neither stimulates [1-¹⁴C]leucine oxidation nor activates the branched-chain α-keto acid dehydrogenase complex of pyruvate-perfused hearts. It is suggested that leucine oxidation by heart is regulated by the activity of the branched-chain α-keto acid dehydrogenase complex which is subject to interconversion between active and inactive forms. Oxidizable substrates establish conditions which inactivate the enzyme. Dichloroacetate, known to activate the pyruvate dehydrogenase complex by inhibition of pyruvate dehydrogenase kinase, causes activation of the branched-chain α-keto acid dehydrogenase complex, suggesting the existence of a kinase for this complex.     

Stability of Lactic Acid Bacteria to Freezing as Related to Their Fatty Acid Composition

The viability of Streptococcus lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h was better preserved when the cells were grown in medium supplemented with oleic acid or Tween 80 (polyoxyethylene sorbitan monooleate). A pronounced change in the cellular fatty acid composition was noted when the bacteria were grown in the presence of Tween 80. In S. lactis the ratio of unsaturated to saturated fatty acids increased from 1.18 to 2.55 and in Lactobacillus sp. A-12 it increased from 0.85 to 1.67 when Tween 80 was added to the growth medium. The antibiotic cerulenin markedly inhibited the growth of lactic acid bacteria in tomato juice (TJ) medium but had almost no effect on the growth of the bacteria in TJ medium containing Tween 80 (or oleic acid). The antibiotic inhibited markedly the incorporation of [1-¹⁴C]acetate but had no inhibitory effect on the incorporation of exogenous [1-¹⁴C]oleate (or [1-¹⁴C]palmitate) into the lipid fractions of lactic acid bacteria. Thus, the fatty acid composition of lactic acid bacteria, inhibited by the antibiotic cerulenin, can be modulated by exogenously added oleic acid (or Tween 80) without the concurrent endogenous fatty acid synthesis from acetate. The data obtained suggest that cerulenin inhibits neither cyclopropane fatty acid synthesis nor elongation of fatty acid acyl intermediates. The radioactivity of cells grown in the presence of [1-¹⁴C]oleate and cerulenin was associated mainly with cyclopropane Δ19:0, 20:0 + 20:1, and 21:0 acids. As a consequence, cerulenin caused a decrease in the ratio of unsaturated to saturated fatty acids in lactic acid bacteria as compared with cells grown in TJ medium plus Tween 80 but without cerulenin. Cerulenin caused a decrease in the viability of S. lactis and Lactobacillus sp. A-12 after freezing at -17°C for 48 h only when Tween 80 was present in the growth medium. We conclude that the sensitivity of lactic acid bacteria to damage from freezing can be correlated with specific alterations in the cellular fatty acids.     

Effect of Tobacco Mosaic Virus Infection on Amino Acid Incorporation into Isolated Mitochondria from Tobacco Leaves

Mitochondria isolated from tobacco leaves incorporated ¹⁴C-leucine into the protein and the rate was enhanced by tobacco mosaic virus (TMV) infection as compared with noninfected level. In vitro amino acid incorporation by mitochondria required adenosine triphosphate (ATP), Mg²⁺, and KC1 and the energy sources from oxidative phosphorylation as well as from ATP-generating system. This incorporation was inhibited by ribonuclease (RNase), deoxyribonuclease (DNase), actinomycin D, mitomycin C, puromycin, and chloramphenicol added in the reaction medium. The pretreatment of the mitochondria with DNase and actinomycin D reduced the rate of incorporation. The mitochondria incorporated ³H-guanosine triphosphate (GTP) and this activity was blocked by actinomycin D. The presence in this system of 15,000 g supernatant cell sap fraction or bacterial contamination was carefully checked obtaining a negative result. The reaction product into which ^l4C-amino acids incorporated was solubilized by trypsin. The nature of the amino acid incorporating activity of isolated mitochondria obtained from TMV-infected tobacco leaves is discussed.     

Catabolism of porphobilinogen by etiolated barley leaves

When [2,4-¹⁴C]porphobilinogen (PBG) or [2 (aminomethyl),5-¹⁴C]PBG is administered to etiolated barley (Hordeum vulgare L. var. Larker) leaves in darkness, label becomes incorporated into CO₂, organic and amino acids, sugars, lipids, and proteins during a 4-hour incubation. Less than 1% of the label, however, is incorporated into porphyrins. The rate of ¹⁴CO₂ evolution from leaves fed [2,4-¹⁴C]PBG is strongly inhibited by anaerobiosis but is unaffected by aminooxyacetic acid, while the rate of ¹⁴CO₂ evolution from [2(aminomethyl),5-¹⁴C]PBG is strongly inhibited by aminooxyacetic acid but is not affected by anaerobiosis.     

Biosynthesis and metabolism of indole-3-ethanol and indole-3-acetic acid by Pinus sylvestris L. needles

Combined gas chromatography-mass spectrometry has been used to identify indole-3-ethanol (IEt) in a purified extract from needles of Pinus sylvestris L. Quantitative estimates obtained by high-performance liquid chromatography with fluorescence detection, corrected for samples losses occurring during purification, indicate that Pinus needles contain 46±4 ng g^-1 IEt. This compares with 24.5±6.5 ng g^-1 indole-3-acetic acid (IAA) and 2.3±0.4 ng g^-1 indole-3-carboxylic acid (ICA) (Sandberg et al. 1984, Phytochemistry, 23, 99–102). Metabolism studies with needles incubated in a culture medium in darkness revealed that both [3-¹⁴C]-tryptophan and [2-¹⁴C]tryptamine mine are converted to [¹⁴C]IEt. It was also shown that [3-¹⁴C]IEt acted as a precursor of [¹⁴C]IAA. The observed metabolism appears to be enzymic in nature. The [2-¹⁴C]IAA was not catabolised to [¹⁴C]ICA in detectable quantities implying that, at best, only a minor portion of the endogenous ICA pool in the Pinus needles originates from IAA.Abbreviations DEAE diethylaminoethyl - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - ICA indole-3-carboxylic acid - IEt indole-3-ethanol - PVP polyvinylpyrrolidone     

A general procedure for the preparation of labeled l-ascorbic acid from labeled d-glucose

A simple, three-step conversion of 1,2-O-isopropylidene-α-d-glucofuranose into l-ascorbic acid, originally described by Bakke and Theander, was used to prepare l-[4-¹⁴C]ascorbic acid from milligram amounts of d-[3-¹⁴C]glucopyranose in 28% radioisotopic yield. In addition, l-[6-¹⁴C]- and l-[U-¹⁴C]-ascorbic acid were prepared from d-[1-¹⁴C]- and d-[U-¹⁴C]-glucopyranose, respectively. The procedure is useful for the synthesis of l-ascorbic acid bearing isotopic hydrogen, carbon, or oxygen atoms at specific positions, subject only to the availability of starting material.     

Peptide conjugates of benzene and toluene metabolites in English ryegrass

Biotransformation of [1-6-¹⁴C]benzene and [1-¹⁴C]toluene in English ryegrass (Lolium perenne L.) seedlings was investigated. Vapors of these compounds were absorbed by the leaves of this plant. Benzene and toluene were oxidized, forming phenol and benzoic acid, respectively. A portion of phenol and benzoic acid was bound by low-molecular-weight peptides forming conjugates. A qualitative amino acid composition of the peptides involved in the conjugation was determined. After removing plants from the atmosphere containing [1-6-¹⁴C]benzene and [1-¹⁴C]toluene, the radioactivity of the conjugates gradually decreased. This process was accompanied by the evolution of ¹⁴CO₂, indicating the breakdown of these conjugates. Radioactive compounds thus formed were oxidized, yielding carbon dioxide. A portion of phenol and benzoic acid, along with peptide conjugation, was subjected to further oxidative transformations up to disruption of the aromatic ring. By this pathway, nonvolatile carboxylic acids, such as muconic, fumaric, succinic, malic, malonic, glycolic, and glyoxylic, were formed. Using electron microscopy, a damaging effect of benzene on the cell ultrastructure of English ryegrass leaves was shown, and this toxic effect depended on the benzene concentration.     

Inhibition of hydrocarbon biosynthesis in the housefly by 2-Octadecynoate

The elongation of [9,10-³H]oleoyl-CoA with malonyl-CoA to form 20, 22, and 24 carbon monounsaturated fatty acids was demonstrated in housefly microsomes by radio-GLC. These elongation reactions, which have been postulated to be involved in hydrocarbon biosynthesis, have not been previously demonstrated in insects. 2-Octadecynoate (18:1 Δ²⁼) inhibited the in vivo incorporation of [1-¹⁴C]acetate into both fatty acids and hydrocarbons in a dose-dependent manner. At doses of 10 μg per female housefly of the alkynoic acid, the incorporation of [1-¹⁴C]acetate into hydrocarbon was inhibited 93%, the incorporation of [9,10-³H]oleate into hydrocarbon was inhibited 64%, and the incorporation of [1-¹⁴C]acetate into total internal lipid was inhibited 65%. Partially purified FAS was inhibited 50% and 95% at 15 μM and 40 μM, respectively, of the alkynoic acid. These results show that 2-octadecynoate inhibits hydrocarbon biosynthesis in the housefly by inhibiting FAS, and the in vivo data suggest that the elongation of 18:1 to longer chain fatty acids is also inhibited.     

Transfer of exogenous auxin from the phloem to the polar auxin transport pathway in pea (Pisum sativum L.)

When [1-¹⁴C]indol-3yl-acetic acid ([1-¹⁴C]IAA) was applied to the upper surface of a mature foliage leaf of garden pea (Pisum sativum L. cv. Alderman), ¹⁴C effluxed basipetally but not acropetally from 30-mm-long internode segments excised 4 h after the application of [1-¹⁴C]IAA. This basipetal efflux was strongly inhibited by the inclusion of 3.10^–6 mol· dm³ N-1-naphthylphthalamic acid (NPA) in the efflux buffer. In contrast, when [¹⁴C] sucrose was applied to the leaf, the efflux of label from stem segments excised subsequently was neither polar nor sensitive to NPA. The [1-¹⁴C]IAA was initially exported from mature leaves in the phloem — transport was rapid and apolar; label was recovered from aphids feeding on the stem; and label was recovered in exudates collected from severed petioles in 20 mM ethylenediaminetetraacetic acid. No ¹⁴C was detected in aphids feeding on the stems of plants to which [1-¹⁴C]IAA had been applied apically, even though the internode on which they were feeding transported considerable quantities of label. Localised applications of NPA to the stem strongly inhibited the basipetal transport of apically applied [1-¹⁴C]IAA, but did not affect transport of [1-¹⁴C]IAA in the phloem. These results demonstrate for the first time that IAA exported from leaves in the phloem can be transferred into the extravascular polar auxin transport pathway but that reciprocal transfer probably does not occur. In intact plants, transfer of foliar-applied [1-¹⁴C]IAA from the phloem to the polar auxin transport pathway was confined to immature tissues at the shoot apex. In plants in which all tissues above the fed leaf were removed before labelling, a limited transfer of IAA occurred in more mature regions of the stem.Abbreviations IAA indol-3yl-acetic acid - EDTA ethylenediaminetetraacetic acid - NPA N-1-naphthylphthalamic acid We are grateful to the Nuffield Foundation for supporting this research under the NUF-URB95 scheme and for the provision of a bursary to A.J.C. We thank Professor Dennis A. Baker for constructive comments on a draft of this paper and Mrs. Rosemary Bell for her able technical assistance.     

The incorporation of [3H]glucosamine, [3H]fucose and [14C]mannose into protein in the rat anterior pituitary incubated in vitro

Rat anterior hemipituitaries incubated in vitro rapidly take up and incorporate into protein D-[6-³H]-glucosamine · HCl, D-[1-¹⁴C]mannose and L-[G-³H]fucose. The newly labeled protein was only slowly released into a Krebs-Ringer bicarbonate incubation medium. Glucosamine- or mannose-labeled protein was barely detectable in the medium after a 30–60 min incubation whereas about 4% of all fucose-labeled protein had already been released into the incubation medium by 30 min. Puromycin · 2HCl (1 mM) inhibited incorporation of glucosamine or mannose into protein to 40% or less of control values within 30 min; fucose incorporation was not significantly inhibited before 45 min. Acid hydrolysis followed by amino acid analysis of glucosamine-labeled protein yielded significant amounts of label in glucosamine, galactosamine and apparent glucosamine-degradation products but no significant amount of label in any amino acid.     

De-novo synthesis and release of peroxidases in cell suspension cultures of Nicotiana tabacum L.

De-novo synthesis of acid and basic peroxidases has been studied in cell suspension cultures of tobacco by incorporation of ³H- and ¹⁴C-amino acids. Incorporation rates were found to be high for acid peroxidases and low for basic peroxidases. Synthesis of all peroxidases was inhibited by cycloheximide and actinomycin D. Subculturing of the cells increased the rates of radioactive amino-acid incorporation into all peroxidases within the first 24 h. This rise in peroxidase synthesis was correlated with the age of the transferred cells. The older the cells were the more pronounced was the effect. During the culture cycle the high rates of peroxidase synthesis at the second day dropped back to initial values. Peroxidase synthesis was thus inversely related to peroxidase accumulation which was very low at the beginning and increased continuously. By pulse-chase experiments it has been shown that newly synthesized acid peroxidases accumulated in the medium. This process was inhibited by monensin. Only the acid peroxidases were secreted into the cell wall and from there released. The basic peroxidases were not detectable in the medium.Abbreviations AA^* radioactive amino-acid mixture - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecyl sulfate     

Oxidation of Fatty Acids by Leishmania braziliensis panamensis1

Heating cultures of Leishmania braziliensis panamensis (grown at 26°C) to 34°C for 1.5–12 h transformed the cells to an ellipsoidally shaped form. The heat treatment caused an increase in the rate of oxidation of both medium and long chain fatty acids but decreased the rate of oxidation of [1-¹⁴C]glucose. The rate of fatty acid oxidation continued to increase for times as long as 20 h after returning the cultures to 26°C. In both the promastigote and heat-induced ellipsoidal forms, the ratio of ¹⁴CO₂ release from [1-¹⁴C]laurate to that from [12-¹⁴C]laurate was generally larger than four, whereas this ratio from [1-¹⁴C]oleate relative to [10-¹⁴C]oleate was approximately two. These data show that metabolic and morphological differentiation begin after a short heat treatment and that some metabolic changes may continue even after the reverse transformation is initiated. The data also suggest that either the ω-terminal portion of the fatty acids is not completely oxidized to acetyl CoA and/or that there are two functional fatty acid oxidation pathways in Leishmania.     

Modification of glycerolipid metabolism in L-M fibroblasts by an unnatural amino-alcohol, N-isopropylethanolamine.

The unnatural amino-alcohol, N-isopropylethanolamine, is incorporated into a phospholipid by monolayers of L-M fibroblasts. This phospholipid was identified as 1,2-diacyl-$\text{sn}$-glycero-3-phosphoisopropylethanolamine by using chemical and enzymatic procedures combined with thin-layer and gas-liquid chromatography. Since the phospho-N-isopropylethanolamine moiety is removed by phospholipase C, the stereochemistry of the phospholipid analog is identical to naturally occurring phosphoglycerides. Incubation of cells in 10 mM N-isopropylethanolamine inhibited the incorporation of [¹⁴C]choline and [¹⁴C]ethanolamine into phospholipids and stimulated the incorporation of [1-¹⁴C]palmitic acid and [1-¹⁴C]hexadecanol into triacylglycerols and alkyldiacylglycerols. These results indicate that N-isopropylethanolamine affects glycerolipid synthesis at the diradylglycerol branch point.