Cucujolide biosynthesis in the merchant and rusty grain beetles

Most known aggregation pheromones of cucujid grain beetles are macrolides called “cucujolides”. It has recently been shown by us that cucujolide I[4(E),8(E)-4,8-dimethyldecadien-10-olide] is of terpenoid origin, and that cucujolide II[3(Z)-dodecen-11-olide] is of fatty acid. The objectives of this study were to determine if farnesol could serve as a precursor of cucujolide I in vivo; to study the conversion of fatty acids to cucujolide II; and to study the stereochemistry of the lactonization reactions leading to cucujolides I and II. Experiments were performed through application of stable isotope-labeling techniques, using the merchant grain beetle, Oryzaephilus mercator (Fauvel), and/or the rusty grain beetle, Cryptolestes ferrugineus (Stephens), as study insects. Exogenous (E,E)-farnesol was converted to cucujolide I. Dual-labeling studies with D and ¹⁸O indicate that this conversion proceeded with retention of the hydroxyl oxygen. Lauric and 11-hydroxydodecanoic acids were not effective precursors of cucujolide II, whereas 3(Z)-dodecenoic acid and 11-hydroxy-3(Z)-dodecenoic acid were effective precursors of cucujolide II. These data support the hypothesis that the biosynthetic route from fatty acids to cucujolide II involves chain shortening through β-oxidation to a 3(Z)-dodecenoic acid intermediate and oxidation at carbon-11 to form a 11-hydroxy-3(Z)-dodecenoic acid intermediate, followed by cylization. Dual-labeling studies with D and ¹⁸O indicate that this cyclization proceeded with retention of the C-11 hydroxyl of the 11-hydroxy-3(Z)-dodecenoic acid intermediate.     

Synthesis of long chain n-3 and n-6 fatty acids having a photoactive conjugated tetraene group

Fatty acids of the n-3 and n-6 families containing a photoactive conjugated tetraene group near the carboxylate were prepared from several naturally occurring fatty acids by sequential iodolactonization and treatment with excess 1,8-diazabicyclo[5.4.0]undec-7-ene. The new conjugated fatty acids include 5E,7E,9E,11Z,14Z- and 5E,7E,9E,11E,14Z-eicosapentaenoic acids derived from arachidonic acid; 5E,7E,9E,11Z,14Z,17Z- and 5E,7E,9E,11E,14Z,17Z-eicosahexaenoic acids from eicosapentaenoic acid; and 4E,6E,8E,10Z,13Z,16Z,19Z- and 4E,6E,8E,10E,13Z,16Z,19Z-docosaheptaenoic acids from docosahexaenoic acid. All of the newly synthesized fatty acids were characterized by UV, ¹H NMR and mass spectroscopy. These new products represent the first examples of directed conjugation of methylene interrupted double bond systems. The products can be synthesized in gram quantities and in high yields (>50%). Interestingly, it did not prove possible to synthesize fatty acids having a triene group near the carboxyl group even using mild conditions and different synthetic approaches. Once initiated, the isomerization always continued until a tetraene group was formed. Because of the sensitivity of the tetraene group to light, these fatty acids have the potential for being used in tracking fatty acid movements in cells employing fluorescence techniques and in UV light-induced cross linking to membrane proteins.     

Identification of a cDNA encoding a novel C18-Δ polyunsaturated fatty acid-specific elongating activity from the docosahexaenoic acid (DHA)-producing microalga, Isochrysis galbana

Isochrysis galbana, a marine prymnesiophyte microalga, is rich in long chain polyunsaturated fatty acids such as docosahexaenoic acid (C22:6n-3, Δ^{4,7,10,13,16,19}). We used a polymerase chain reaction-based strategy to isolate a cDNA, designated IgASE1, encoding a polyunsaturated fatty acid-elongating activity from I. galbana. The coding region of 263 amino acids predicts a protein of 30 kDa that shares only limited homology to animal and fungal proteins with elongating activity. Functional analysis of IgASE1, by expression in Saccharomyces cerevisiae, was used to determine its activity and substrate specificity. Transformed yeast cells specifically elongated the C18-Δ⁹ polyunsaturated fatty acids, linoleic acid (C18:2n-6, Δ^9,12) and -linolenic acid (C18:3n-3, Δ^9,12,15), to eicosadienoic acid (C20:2n-6, Δ^11,14) and eicosatrienoic acid (C20:3n-3, Δ^11,14,17), respectively. To our knowledge this is the first time such an elongating activity has been functionally characterised. The results also suggest that a major route for eicosapentaenoic acid (C20:5n-3, Δ^5,8,11,14,17) and docosahexaenoic acid syntheses in I. galbana may involve a Δ⁸ desaturation pathway.     

Moth desaturase characterized that produces both Z and E isomers of delta 11-tetradecenoic acids

The redbanded leafroller moth, Argyrotaenia velutinana (Lepidoptera: Tortricidae) uses a 92:8 mixture of (Z)-11- and (E)-11-tetradecenyl acetate in its pheromone blend. These are produced in the abdominal pheromone gland from the corresponding acids, which are biosynthesized in the gland in a 3:2 Z/E ratio by desaturation of myristoyl CoA. The delta 11 desaturase involved in this reaction exhibits unusual substrate and stereospecificities in specifically producing Z11 and E11 isomers of tetradecenoic acid, and exhibiting no activity with C16 and C18 precursor acids. This report describes the cloning and expression of the redbanded leafroller moth delta 11 desaturase, and compares its amino-acid sequence to those of other known insect Z9, Z10, Z11, and E11 desaturases. The metabolic Z9 desaturase from fat body tissue also was cloned and expressed, and found mainly to produce Z9-16:Acid and Z9-18:Acid. The open reading frame of the delta 11 desaturase encodes a protein with 329 amino acids, whereas the open reading frame of the Z9 desaturase encodes a protein with 351 amino acids. Addition of this new delta 11 desaturase with its different substrate and regiospecificites to the databank of characterized integral-membrane desaturases will be key in efforts to determine amino-acid mutations responsible for the wide array of unsaturated fatty-acid products.     

Comparative study of sex pheromone composition and biosynthesis in Helicoverpa armigera, H. assulta and their hybrid

Two Helicoverpa species, H. armigera and H. assulta use (Z)-11-hexadecenal and (Z)-9-hexadecenal as their sex attractant pheromone components but in opposite ratios. Since both female and male interspecific hybrids produced by female H. assulta and male H. armigera have been obtained in our laboratory, we can make a comparative study of sex pheromone composition and biosynthesis in the two species and their hybrid. With GC and GC-MS analyses using single gland extracts, the ratio of (Z)-9-hexadecenal to (Z)-11-hexadecenal was determined as 2.1:100 in H. armigera, and 1739:100 in H. assulta. The hybrid has a ratio of 4.0: 100, which is closer to that of H. armigera, but significantly different from H. armigera. We investigated pheromone biosynthesis with labeling experiments, using various fatty acid precursors in H. armigera, H. assulta and the hybrid. In H. armigera, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation; (Z)-9-hexadecenal results from delta11 desaturation of stearic acid, followed by one cycle of chain shortening, reduction and terminal oxidation. delta11 desaturase is the unique desaturase for the production of the two pheromone components. In our Chinese strain of H. assulta, palmitic acid is used as the substrate to form both the major pheromone component, (Z)-9-hexadecenal and the minor one, (Z)-11-hexadecenal. Our data suggest that delta9 desaturase is the major desaturase, and delta11 desaturase is responsible for the minor component in H. assulta, which is consistent with previous work. However, the weak chain shortening acting on (Z)-9 and (Z)-11-octadecenoic acid, which is present in the pheromone glands, does occur in this species to produce (Z)-7 and (Z)-9-hexadecenoic acid. In the hybrid, the major pheromone component, (Z)-11-hexadecenal is produced by delta11 desaturation of palmitic acid, followed by reduction and terminal oxidation. The direct fatty acid precursor of the minor component, (Z)-9-hexadecenoic acid is mainly produced by delta9 desaturation of palmitic acid, but also by delta11 desaturation of stearic acid and one cycle of chain shortening. The greater relative amounts of (Z)-9-hexadecenal in the hybrid are due to the fact that both palmitic and stearic acids are used as substrates, whereas only stearic acid is used as substrate in H. armigera. The evolutionary relationships between the desaturases in several Helicoverpa species are also discussed in this paper.     

Variations in the activity of fatty ACYL-CoA desaturases and electron-transport components in Tetrahymena microsomes with temperature and age of culture

1. 1.|Alterations in the fatty acid composition of microsomes were most marked in the exponential phase of both 39.5- or 15°C- grown Tetrahymena pyriformis NT-1.

2. 2.|Activities of palmitoyl-CoA and stearoyl-CoA desaturases were lower in 15°C cells than in 39.5°C cells, while the activity of oleoyl-CoA desaturase was higher in 15°C cells.

3. 3.|Activities of the terminal component of the desaturation system as well as all three desaturases (palmitoyl-CoA, stearoyl-CoA, oleoyl-CoA) were higher in the exponential phase than in the stationary phase for cells grown at both temperatures.

4. 4.|NAD(P)H-cytochrome c reductase activity and cytochrome b₅ content were reduced whereas NADH-ferricyanide reductase activity was increased in the stationary phase at both 39.5 and 15°C.

Stereospecificity of the (Z)-9 desaturase that converts (E)-11-tetradecenoic acid into (Z,E)-9,11-tetradecadienoic acid in the biosynthesis of Spodoptera littoralis sex pheromone

Moth pheromone glands contain desaturases that catalyze the formation of conjugated dienoic fatty acids. In this article we present the first stereochemical study on one of these enzymes, namely the Delta(9) desaturase of (E)-11-tetradecenoic acid, using the moth Spodoptera littoralis as a biological model and enantiopure deuterated probes derived from tridecanoic acid. Gas chromatography coupled to mass spectrometry analysis of methanolyzed lipidic extracts from glands incubated with each individual probe showed that in the transformation of (E)-11-tetradecenoic acid into (Z,E)-9,11-tetradecadienoic acid both pro-(R) hydrogen atoms at C9 and C10 are removed from the substrate.     

Biosynthesis of 10,12-dienoic fatty acids by a bifunctional Delta11 desaturase in Spodoptera littoralis

In the biosynthetic pathway of Spodoptera littoralis sex pheromone, (E,E)-10,12-tetradecadienoic acid is produced from (Z)-11-tetradecenoic acid by desaturation and concomitant migration of the precursor double bond. With the aim of identifying the enzyme involved in this biotransformation, yeast Deltaelo1/Deltaole mutants, which are both elongase 1 and Delta9 desaturase-deficient, were transformed with the S. littoralis Delta11 desaturase gene using a Cu+2 inducible expression vector. The transformants produced a recombinant polyhistidine-tagged Delta11 desaturase that could be detected by immunoblotting from cell lysates. Lipid analysis revealed that besides producing large quantities of C11-monounsaturated fatty acids, mainly (Z)-11-hexadecenoic acid, (E,E)-10,12-tetradecadienoic acid and minor amounts of (E,Z)-10,12-hexadecadienoic acid were also produced, as well as very low quantities of another tetradecadienoate, which was tentatively identified as the (E,Z)-10,12-tetradecadienoic isomer. None of these dienes was detected with the Delta11 desaturase gene of Trichoplusia ni, which does not produce conjugated dienes as pheromone components. We conclude that the Delta11 desaturase of S. littoralis is a bifunctional enzyme with both Delta11 and Delta10,12 desaturation activities. The relationship between the substrate structure and the stereochemical outcome of the reaction is discussed.     

Inhibition of the acyl-CoA desaturases involved in the biosynthesis of Spodoptera littoralis sex pheromone by analogs of 10,11-methylene-10-tetradecenoic acid

The desaturase inhibitory activity of the cyclopropenyl alcohols 9,10-methylene-9-tetradecen-1-ol (9-MTOL), 10,11-methylene-10-tetradecen-1-ol (10-MTOL) and 11,12-methylene-11-tetradecen-1-ol (11-MTOL), which are structural analogs of 10,11-methylene-10-tetradecenoic acid (10-MTA), is reported. At equimolar ratios with respect to the different substrates, the three compounds completely inhibited the three desaturation reactions involved in the biosynthesis of Spodoptera littoralis sex pheromone. The dose-dependence of inhibition was determined for 10-MTA and its alcohol derivative. Both compounds inhibited the transformation of perdeuterated palmitic acid into perdeuterated (Z)-11-hexadecenoic acid and that of (E)-11-tridecenoic acid into (Z,E)-9,11-tridecadienoic acid with similar IC(50) values. The overall results presented in this work support scattered data that neither the free carboxyl groups nor their acyl-CoA esters are a requisite for inhibition of desaturases. Since the synthesis of cyclopropenols is much more convenient than that of cyclopropene fatty acids, this finding is of economical relevance regarding the putative use of cyclopropene derivatives in pest control.     

Determination of free energies in reaction centers of Rb. sphaeroides

Magnetic field-dependent recombination measurements together with magnetic field-dependent triplet lifetimes (Chidsey, E.D., Takiff, L., Goldstein, R.A. and Boxer, S.G. (1985) Proc. Natl. Acad. Sci USA 82, 6850–6854) yield a free energy change ΔG(P⁺H⁻ − ³P*) = 0.165 eV ±0.008 at 290 K. This does not depend on whether nuclear spin relaxation in the state ³P* is assumed to be fast or slow compared to the lifetime of this state. This value, being (almost) temperature independent, indicates ΔG(P⁺H⁻ − ³P*) ΔH(P⁺H⁻ − ³P*) and is consistent with ΔG(¹P* − P⁺H⁻) and ΔH(¹P* − ³P*) from previous delayed fluorescence and phosphorescence data, implying ΔG ΔH for all combinations of these states.     

Viscous energy dissipation in a model of the human bronchial tree

The viscous energy dissipation in a two generation model of the human bronchial tree is determined from inspiratory velocity and static pressure data obtained for large Reynolds numbers (10⁴ < Re < 10⁵). This dissipation is found to be an increasing function of both Re and distance downstream from the inlet of the model. The ratio of the dissipation in the model to the energy dissipation in an equivalent straight pipe system is determined. This ratio, Z^*, for the model is compared to values in the literature for lower (laminar) Re. There is more dissipation in the branched model than in a straight pipe (Z^* > 1) and turbulence keeps Z^* at roughly a fixed value for large Reynolds numbers (10⁴ < Re < 10⁵). Z^* values for curved pipes are also compared to the branching system values. It is found that the energy dissipation for the branched model behaves similarly to that in curved pipes.     

Synthesis and characterization of SrCu2(O2CR)3(bdmap)3 and Bi2(O2CCH3)4(bdmap)2(H2O) (R = CH3, CF3; bdmap = 1,3-bis(dimethylamino)-2-propanolato)

New mixed metal complexes SrCu₂(O₂CR)₃(bdmap)₃ (R = CF₃ (1a), CH₃ (1b)) and a new dinuclear bismuth complex Bi₂(O₂CCH₃)₄(bdmap)₂(H₂O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF₂ and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi₂O₃ at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2J = 34.0(8) cm⁻¹. Crystal data for 1a: C₂₇H₅₁N₆O₉F₉Cu₂Sr/THF, monoclinic space group P2₁/m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) ų, Z = 2; for 1b: C₂₇H₆₀N₆O₉Cu₂Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) ų, Z = 8; for 2: C₂₂H₄₈O₁₁N₄Bi₂, monoclinic space group P2₁/c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) ų, Z = 4.     

Δ-THC and 11-OH-Δ-THC: Behavioral effects and relationship to plasma and brain levels

The time course of effects following i.p. injections of 0.3–10.0 mg/kg Δ⁹-tetrahydrocannabinol (δ⁹-THC) and 0.1–3.0 mg/kg 11-OH-Δ⁹-THC were determined in rats during 6 hour sessions under a fixed-interval 90-second schedule of food reinforcement. In addition, the acute and chronic effects of these two drugs were tested in different rats trained on a differential reinforcement of low rate 15-second schedule. The onset of activity of 11-OH-Δ⁹-THC was faster, and usually abruptly suppressed all responding, while Δ⁹-THC's onset was slower and often resulted in a decreased and steady pattern of responding. 11-OH-Δ⁹-THC was about 3 times more potent, had a shorter duration of effect and when responding resumed, it returned to control rates within a shorter time than for Δ⁹-THC. Tolerance and cross-tolerance developed at the same rate to equipotent doses of the two drugs. The time course for plasma and brain levels of radioactivity were studied in other rats after i.p. administration of H³-Δ⁹-THC and H³-11-OH-Δ⁹-THC. 11-OH-Δ⁹-THC was absorbed more quickly than Δ⁹-THC and reached peak plasma and brain levels earlier. In addition, higher plasma and brain levels, and larger brain to plasma ratio of radioactivity were attained after 11-OH-Δ⁹-THC. Therefore, differences in behavioral effects produced by Δ⁹-THC and it's 11-hydroxy metabolite were accompanied by differences in absorption and disposition.     

Differential inhibition of fungal oxidosqualene cyclase by 6E and 6Z isomers of 2,3-epoxy-10-aza-10,11-dihydrosqualene

Inhibitory properties of 6E (compound 1) and 6Z (compound 2) isomers of 2,3-epoxy-10-aza-10,11-dihydrosqualene against oxidosqualene-lanosterol cyclase were assayed on microsomes and whole cells of Saccharomyces cerevisiae and Candida albicans. Only the 6E isomer (compound 1), bearing a correct substrate-like configuration, strongly inhibited the enzyme both in microsomes and cell cultures. The difference between compounds 1 and 2 (which had an unfavorable geometry) was especially evident when measuring [¹⁴C]acetate incorporation into non-saponifiable lipids extracted from treated cells. While isomer Z was totally ineffective at up to 30 μM, in cells treated with 5 μM isomer E, labelled oxidosqualene, the level of which was negligible in the control, rose to over 60% of the non-saponifiable lipids.     

基于重组毕赤酵母的fusaruside生物合成

目的:构建产fusaruside的毕赤酵母菌株,解决天然小分子免疫抑制剂fusaruside的来源问题。方法:从禾谷镰刀菌Fusarium graminearum PH-1中扩增获得合成fusaruside的相关基因-3位去饱和酶[Δ3(E)-SD]和10位去饱和酶[Δ10(E)-SD]基因;并通过2A肽策略构建两种基因的共表达载体,转化到毕赤酵母GS115中进行双酶的诱导表达;对诱导后的毕赤酵母菌体进行甲醇和二氯甲烷的处理后,经高效液相色谱质谱联用仪(HPLC-MS)检测其中产物变化。结果:3位去饱和酶和10位去饱和酶在毕赤酵母中成功共表达,SDS-PAGE显示3位去饱和酶分子量约为48kDa,10位去饱和酶分子量约为65kDa; HPLC-MS显示重组酵母可以产生fusaruside。结论:与fusaruside原产菌株镰刀菌相比,该酵母菌的发酵时间更短、产量更高,为fusaruside的进一步开发与应用奠定基础。     

Absolute configurations of pittosporatobiraside A and B from Pittosporum tobira

The absolute configuration at C-12 of pittosporatobiraside A and B isolated from the leaves of Pittosporum tobira was determined to be S on the basis of the exciton chirality of their dibenzoate derivative. The structures of the two glycosides were thus established to be (1S,9S,10S,11S,12S,14R,16R)-12-[(Z)-2-methyl-1-oxo-2-butenyl]-6,14-dimethyl-2-methylene-9-(1-methylethyl)-15,17-dioxatricyclo[8.7.0.0^11,16]heptadec-5-en-13-one and (1S,9S,10S,11S,12S,14R,16R)-12-(3-methyl-1-oxo-2-butenyl)-6,14-dimethyl-2-methylene-9-(1-methylethyl)-15,17-dioxatricyclo [8.7.0.0^11,16]heptadec-5-en-13-one, respectively.     

Kinetics and mechanisms of ligand substitution reactions of molybdenum SO2 complexes. Synthesis and X-ray structure of trans-Mo(CO)2 (dmpe) (PPh3) (SO2)

Kinetic results are reported for intramolecular PPh₃ substitution reactions of Mo(CO)₂(η¹-L)(PPh₃)₂(SO₂) to form Mo(CO)₂(η²-L)(PPh₃)(SO₂) (L = DMPE = (Me)₂PC₂H₄P(Me)₂ and dppe=Ph₂PC₂H₄PPh₂) in THF solvent, and for intermolecular SO₂ substitutions in Mo(CO)₃(η²-L)(η²-SO₂) (L = 2,2′-bipyridine, dppe) with phosphorus ligands in CH₂Cl₂ solvent. Activation parameters for intramolecular PPh₃ substitution reactions: ΔH^≠ values are 12.3 kcal/mol for dmpe and 16.7 kcal/mol for dppe; ΔS^≠ values are −30.3 cal/mol K for dmpe and −16.4 cal/mol K for dppe. These results are consistent with an intramolecular associative mechanism. Substitutions of SO₂ in MO(CO)₃(η²-L)(η²-SO₂) complexes proceed by both dissociative and associative mechanisms. The facile associative pathways for the reactions are discussed in terms of the ability of SO₂ to accept a pair of electrons from the metal, with its bonding transformations of η²-SO₂ to η¹-pyramidal SO₂, maintaining a stable 18-e count for the complex in its reaction transition state. The structure of Mo(CO)₂(dmpe)(PPh₃)(SO₂) was determined crystallographically: P2₁/c, A=9.311(1), B = 16.344(2), C = 18.830(2) Å, ß=91.04(1)°, V=2865.1(7) ų, Z=4, R(F)=3.49%.