bluuebunny/crossref_metadata_2025_split huggingface dataset:
A micro enzymic method for determination of choline‐containing phospholipids in serum and high density lipoproteins
Authors: Nie Ying , He Jin Lin , Hsia S. L. 
Published: November 2006

AbstractA micro method is described for the assay of choline‐containing phospholipids in serum and high density lipoproteins (HDL) using an automated microtiter plate reader. The method is adapted from the enzymic method of Takayama, Itoh, Nagasaki, and Tanimuzu (Clin. Chim. Acta 79, 93–98, 1977) using phospholipase D, choline oxidase, and peroxidase coupled with the color generating system phenol and 4‐amino‐antipyrine. The micro method requires 5 μL of serum or HDL sample, and 42 samples can be assayed in duplicate in one run using a 96‐well flat‐bottom microtiter plate. The reaction is linear up to 400 mg/dL and the lower limit of detection is 0.25 mg of choline‐containing phospholipids per assay. The coefficient of variation within an assay is 0.86–0.79%, and day‐to‐day variation is 0.9–1.5%. Results obtained by the micro method are in excellent agreement with those obtained by the procedure of Takayamaet al. (r=0.997). The supernatant left after removal of low density lipoproteins and very low density lipoproteins from serum and precipitation with heparin/manganese chloride reagent can thus be conveniently used for the micro assay of choline phospholipids in HDL.
Peroxisomes in mice fed a diet supplemented with low doses of fish oil
Authors: Van den Branden C. , De Craemer D. , Pauwels M. , Vamecq J. 
Published: November 2006

AbstractThe influence of low dietary doses (0.1 and 0.8% w/w) of a commercial fish oil preparation on peroxisomes in normal mice was studied and compared to the known strong inductive effects of high (10%) fish oil diets. Low fish oil doses were chosen to supply the mice with a concentration of docosahexaenoic acid, which was beneficial to patients with a peroxisomal disease. Peroxisomes were evaluated by cytochemical, morphometric, and enzymological techniques. The 0.1% fish oil diet had no effect on peroxisomes in liver, heart, and kidney even after prolonged treatment. The 0.8% diet did not change the peroxisomal number nor the catalase (EC 1.11.1.6) activity in the liver. Hepatic peroxisomal β‐oxidation, however, was increased by 50% after 14 d. This was accompanied by reduced peroxisomal size. The 0.8% diet also caused a small increase (+25%) in myocardial catalase activity. No effect was observed in kidneys. Our results indicate that in mice a low (<0.8%) dietary fish oil dose has no or only a slight effect on hepatic peroxisomal β‐oxidation. This may be of particular interest to patients with a peroxisomal fatty acid β‐oxidation defect and who display a severe deficiency of docosahexaenoic acid—diets supplemented with low fish oil doses will improve the docosahexaenoic acid level without adding a strong load to the disturbed fatty acid metabolism.
Phospholipid molecular species composition of developing fetal guinea pig brain
Authors: Burdge Graham C. , Postle Anthony D. 
Published: November 2006

AbstractAdequate accumulation of polyunsaturated essential fatty acids, in particular docosahexaenoic acid (22∶6n−3), into membrane phospholipids is critical for optimal fetal brain development. This process is maximal during the period of rapid neurite outgrowth, neuritogenesis, which precedes the major growth phase, myelination. There is no information about differential changes during gestation to individual brain phospholipid molecular species which contain 22∶6n−3. Such details of brain development would be concealed by total fatty acid analysis of isolated phospholipid classes. We have detailed phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecular species compositions in developing fetal guinea pig brain. Total brain PC concentration increased substantially between 40 and 68 (term) d of gestation, corresponding to myelination, while PE increased in a biphasic manner between 25–35 d, which was coincident with onset of neuritogenesis, and 40–68 d. Fetal brain development was accompanied by complex changes in the concentration of individual phospholipid molecular species. During early gestation (25–40 d) 22∶6n−3 was enriched in both PC and PEsn−1 16∶0 molecular species. However, between 40 d and term there was no further increase in brain PC 22∶6n−3 content, while brain PE was significantly enriched in both PE 18∶1/22∶6 and PE18∶0/22∶6. We hypothesize that accumulation of 22∶6n−3 intosn−1 18∶1 and 18∶0 species represents establishment of a 22∶6n−3‐containing membrane PE pool which may be turned over more slowly thansn−1 16∶0 species. Identification of specific changes in membrane phospholipids which are associated with defined events in brain development may provide a basis for assigning functional roles to individual molecular species.
Cucumber cotyledon lipoxygenase oxygenizes trilinolein at the lipid/water interface
Authors: Matsui K. , Kajiwara T. 
Published: November 2006

AbstractThe reactivity of cucumber cotyledon lipoxygenase with trilinolein was examined. The activity of the enzyme against linoleic acid rapidly decreased with increasing pH of the assay solution, and essentially no activity could be detected above pH 8.5. The rapid decrease in activity was not the result of an inactiveness of the enzyme at alkaline pH, because with trilinolein, the enzyme showed a broad pH‐activity profile, and substantial activity could be detected even at pH 9.0. Rather, the decrease in activity was due to the dissociation of the linoleic acid emulsion into acid‐soap aggregates and/or the monomeric form, depending on the ionization of the terminal carboxylic group. This suggests that cucumber cotyledon lipoxygenase acts only on an insoluble substrate at the lipid/water interface but not on a soluble one. High‐performance liquid chromatography analyses of the products formed from trilinolein revealed that the enzyme inserted oxygen into the acyl moiety of trilinolein without hydrolysis of the ester bonds. Preincubation of the enzyme with triolein emulsions effectively abolished its activity against trilinolein added afterward. Furthermore, the enzyme was adsorbed on the trilinolein or triolein emulsion droplets in an essentially irreversible manner. A reaction velocity curve of the enzyme with trilinolein showed saturation kinetics. This is thought to be due to a regional substrate deficiency as the reaction proceeds. These lines of evidence indicate that the enzyme, once bound to the lipid/water interface, is unable to break free and bind to other emulsions.
Inhibition of neutral cholesteryl ester hydrolase by the glycolytic enzyme enolase. Is this a secondary function of enolase?
Authors: Shand John H. , West David W. 
Published: November 2006

AbstractThere is an accumulation of the glycolytic enzyme enolase and of cholesteryl esters in macrophages that have been converted into “foam” cells. In this study, we questioned whether enolase could be involved in this accumulation of cholesteryl esters by inhibiting the activity of neutral cholesteryl ester hydrolases. Enolase from both yeast and rabbit muscle were incubated with three different cholesteryl ester hydrolases and were shown to inhibit the hydrolysis of cholesteryl esters. Inhibition was dependent on the concentration of enolase and appeared to occur through binding of the enolase to the cholesteryl ester. Nevertheless, the yeast and rabbit muscle enolases differed in their efficiency of inhibition and in their mechanism of action. Purification of commercial enolase preparations by gel‐filtration yielded single proteins with the same inhibitory activities as the originals, indicating that the inhibition was not due to the presence of an impurity. Partially purified αα‐and γγ‐isoforms of the enzyme from rat brain also appear to have inhibitory effects on cholesteryl ester hydrolysis. Negative control of the hydrolytic phase of the cholesterol/cholesteryl ester cycle may be a secondary function of enolases which correlates with the accumulation of cholesteryl esters in a number of neuro‐degenerative and demyelinating diseases.
Tissue‐selective inhibition of sterol synthesis in mice by pravastatin sodium after a single or repeated oral administrations
Authors: Koga Teiichiro , Kikuchi Takashi , Miyazaki Atsuhiro , Koike Hiroyuki 
Published: November 2006

AbstractPravastatin, an inhibitor of 3‐hydroxy‐3‐methylglutaryl CoA (HMG‐CoA) reductase, exhibits liver‐selectivity in inhibiting sterol synthesis, when administered as a single oral dose to mice or rats, whereas lovastatin and simvastatin do not. This may be due to the fact that pravastatin is distributed intracellularly, to a large extent, in the liver and extracellularly in nonhepatic tissues. In the present study, we examined whether the difference in liver‐selectivity among these three HMG‐CoA reductase inhibitors observed in single‐dose studies was preserved after repeated oral administrations of drugs to mice.De novo sterol synthesis in different tissues of mice was examinedin vivo three hours after the last dose of drug by measuring incorporation of intraperitoneally injected [14C]acetate into total sterols. Pravastatin administered orally for 11 consecutive days at 5 and 10 mg/kg exhibited a greater liver‐selectivity than lovastatin and simvastatin: sterol synthesis was inhibited more than 60% in the liver by all three drugs, whereas that in nonhepatic tissues was inhibited less than 10% by pravastatin and more than 30% by lovastatin and simvastatinin in most of the nonhepatic tissues examined. Pravastatin administered orallyfor 11 consecutive days at 10 mg/kg caused more selective inhibition of sterol synthesis in liverex vivo than two other inhibitors at the same dose. Pravastatin inhibitedde novo sterol synthesis from [14C]acetate into sterol fraction in the liver slicesin vitro, but minimally in those of the spleen and testis, whereas lovastatin and simvastatin inhibited in those of all three tissues. Since the drug concentrations determined in the same tissue samples of the liver, spleen, and testis were almost comparable among the three drugs, it was suggested that the cellular distribution profiles of pravastatin observed in a single‐dose study were preserved in the multiple‐dose study. We conclude that the difference in tissue‐selectivity between pravastatin and the other two inhibitors to inhibit sterol synthesis in mice is maintained, regardless of the duration of administration.
Some new aspects of isoprenoid biosynthesis in plants—A review
Authors: Bach Thomas J. 
Published: November 2006

AbstractPlants are capable of synthesizing a myriad of isoprenoids and prenyl lipids. Much attention has been focused on 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMGR), the enzyme that synthesizes mevalonate and is generally considered responsible for the regulation of substrate flux to isoprenoids. In contrast to vertebrates, where there seems to exist only one HMGR gene, in plants a small family of isogenes appears differentially expressed in regard to location and time. Much less is known in plants about the preceding steps,viz. the conversion of acetyl‐CoA to HMG‐CoA. An enzyme system has been isolated from radish that can catalyze this transformation, and which shows some unusual propertiesin vitro. The intracellular localization of the early steps of isoprenoid biosynthesis in plant cells is still a matter of debate. The various observations and hypotheses derived from incorporation and inhibition studies are somewhat contradictory, and an attempt is being made to rationalize various findings that do not at first seem compatible. There are good arguments in favor of an exclusively cytoplasmic formation of isopentenyl pyrophosphate (IPP) via mevalonic acid, but other studies and observations suggest an independent formation in plastids. Other possibilities are being considered, such as the existence of independent (compartmentalized) biosynthetic pathways of IPP formationvia the socalled Rohmer pathway. Substrate channeling through the formation of end product‐specific multienzyme complexes (metabolons) with no release of substrate intermediates will also be discussed.
Developmental regulation of sterol biosynthesis inZea mays
Authors: Guo De‐an , Venkatramesh M. , Nes W. David 
Published: November 2006

AbstractSixty‐one sterols and pentacyclic triterpenes have been isolated and characterized by chromatographic and spectral methods fromZea mays (corn). Several plant parts were examined; seed, pollen, cultured hypocotyl cells, roots, coleoptiles (sheaths), and blades. By studying reaction pathways and mechanisms on plants fed radiotracers ([2‐14C]mevalonic acid, [2‐14C]acetate, and [2‐3H]acetate), and stable isotopes (D2O), we discovered that hydroxymethylglutaryl CoA reductase is not “the” rate‐limiting enzyme of sitosterol production. Additionally, we observed an ontogenetic shift and kinetic isotope effect in sterol biosynthesis that was associated with the C‐24 alkylation of the sterol side chain. Blades synthesized mainly 24α‐ethyl‐sterols, sheaths synthesized mainly 24‐methyl‐sterols, pollen possessed an interrupted sterol pathway, accumulating 24(28)‐methylene‐sterols, and germinating seeds were found to lack an activede novo pathway. Shoots, normally synthesizing (Z)‐24(28)‐ethylidine‐cholesterol, after incubation with deuterated water, synthesized the rearranged double‐bond isomer, stigmasta‐5,23‐dien‐3β‐ol. Examination of the mass spectrum and1H nuclear magnetic resonance spectrum of the deuterated 24‐ethyl‐sterol indicated the Bloch‐Cornforth route originating with acetyl‐CoA and passing through mevalonic acid to sterol was not operative at this stage of development. An alternate pathway giving rise to sterols is proposed.
Cloning of the late genes in the ergosterol biosynthetic pathway ofSaccharomyces cerevisiae—A review
Authors: Lees N. D. , Skaggs B. , Kirsch D. R. , Bard M. 
Published: November 2006

AbstractResearch on the ergosterol biosynthetic pathway in fungi has focused on the identification of the specific sterol structure required for normal membrane structure and function and for completion of the cell cycle. The pathway and its end product are also the targets for a number of antifungal drugs. Identification of essential steps in ergo‐sterol biosynthesis could provide new targets for the development of novel therapeutic agents. Nine of the eleven genes in the portion of the pathway committed exclusively to ergosterol biosynthesis have been cloned, and their essentiality for aerobic growth has been determined. The first three genes;ERG9 (squalene synthase),ERG1 (squalene epoxidase), andERG7 (lanosterol synthase), have been cloned and found to be essential for aerobic viability since their absence would result in the cell being unable to synthesize a sterol molecule. The remaining eight genes encode enzymes which metabolize the first sterol, lanosterol, to ultimately form ergosterol. The two earliest genes,ERG11 (lanosterol demethylase) andERG24 (C‐14 reductase), have been cloned and found to be essential for aerobic growth but are suppressed by mutations in the C‐5 desaturase (ERG3) gene andfen1 andfen2 mutations, respectively. The remaining cloned genes,ERG6 (C‐24 methylase),ERG2 (D8Æ7 isomerase),ERG3 (C‐5 desaturase), andERG4 (C‐24(28) reductase), have been found to be nonessential. The remaining genes not yet cloned are the C‐4 demethylase and the C‐22 desaturase (ERG5).
Biochemical and physiological effects of sterol alterations in yeast—A review
Authors: Parks Leo W. , Smith Steven J. , Crowley James H. 
Published: November 2006

AbstractConsiderable progress has been made in the selection and characterization of mutants that are defective in the synthesis of ergosterol in the yeast,Saccharomyces cerevisiae. Mutations in nearly every step of the yeast sterol biosynthetic pathway have been induced and selected. These mutants have been used to elucidate the sequential order of steps in sterol synthesis, to study the mode of action of antifungal agents and to determine the method of resistance of some pathogenic fungi, and to answer questions on the role of sterols in general cell biology. Physiological examination of ergosterol null mutants, lacking all biochemical activity attributed to the particular gene, supports a role for ergosterol in a number of critical functions in the organism. Among the physiological functions attributed to ergosterol are sparking and bulking requirements, involvement in amino acid and pyrimidine transport, resistance to antifungal agents and certain cations, and a requirement for respiratory activity. Those genetic null alleles discussed in this review areerg24, lacking the ability to reduce the Δ14 double bond;erg6, unable to methylate C‐24; anderg3, defective in the C‐5 desaturase. The different biochemical activities that are disrupted in the ergosterol mutants support a role for ergosterol in a number of critical functions in yeast.
Identification of the active site of vertebrate oxidosqualene cyclase
Authors: Abe Ikuro , Prestwich Glenn D. 
Published: November 2006

AbstractActive site mapping of rat liver oxidosqualene cyclase (OSC), a 78 kDa membrane‐bound enzyme, was carried out using the mechanism‐based irreversible inhibitor, [3H]29‐methylidene‐2,3‐oxidosqualene. The amino acid sequence of the radiolabeled CNBr peptide fragment showed unexpectedly high similarity to the yeast OSC, plant OSC, and bacterial squalene cyclases. Further, radio analysis established that the two adjacent Asp residues in the highly conserved region (Asp‐Asp‐Thr‐Ala‐Glu‐Ala, or DDTAEA) were equally labeled by the irreversible inhibitor. This result provided the first information on the structural details of the active site of OSC, and showed for the first time the ancient lineage of this vertebrate enzyme to ancestral eukaryotic and prokaryotic cyclases. Interestingly, the covalently‐modified DDXX(D/E) sequence of rat liver OSC showed surprising similarity to the putative allylic diphosphate binding site sequence of other terpene cyclases and prenyl transferases. The Asp‐rich motif may act as a point charge to stabilize incipient cationic charge.
Biosynthesis and distribution of insect‐molting hormones in plants—A review
Authors: Adler John H. , Grebenok Robert J. 
Published: November 2006

AbstractInsect‐molting hormones, phytoecdysteroids, have been reported to occur in over 100 plant families. Plants, unlike insects, are capable of the biosynthesis of ecdysteroids from mevalonic acid, and in several cases the biosynthesis of phytoecdysteroids was also demonstrated to proceedvia sterols.Spinacia oleracea (spinach) biosynthesizes polypodine B and 20‐hydroxyecdysone, which is the predominant insect‐molting hormone found in plant species. The onset of ecdysteroid production in spinach requires the appropriate ontogenetic development within the plant, which is related to leaf development. In spinach, lathosterol is the biosynthetic precursor to ecdysone and 20‐hydroxyecdysone. Phosphorylated ecdysteroid intermediates, particularly ecdysone‐3‐phosphate, are required during biosynthesis. Polyphosphorylated forms of ecdysteroids are putative regulatory components of the pathway. During spinach development, the 20‐hydroxyecdysone is transported from the sites of biosynthesis to the apical regions. An analysis of the physiological data available suggests that different species may synthesize ecdysteroids in various organs and distribute these ecdysteroids to other sites. Annual plants appear to concentrate ecdysteroids in the apical regions, including flowers and seeds. Perennial plants may recycle their ecdysteroids between their deciduous and their perennial organs over the growing season. Further investigations of ecdysteroid biosynthesis and physiology within plants will be required before an acceptable system can be designed to test phytoecdysteroid effectivenessin vivo against insect herbivory.
Sterol metabolism in the tobacco hornworm,Manduca sexta—A review
Authors: Svoboda James A. , Weirich Gunter F. 
Published: November 2006

AbstractA number of intermediates involved in the dealkylation and conversion of the major C28 and C29 phytosterols to cholesterol in insects were first isolated and identified in studies with the tobacco hornworm,Manduca sexta, carried out in our laboratory. We also investigated the effects of a variety of known sterol metabolism inhibitors inManduca, particularly those affecting the Δ24‐sterol reductase enzyme, and synthesized and tested a number of new inhibitors as well. In‐depth studies of ecdysteroids inManduca during embryogenesis and during pupal‐adult development provided new information on molting hormone content, biosynthesis, and metabolism. In addition, this insect has been utilized in the study of three specific enzyme systems of ecdysteroid metabolism, namely 20‐monooxygenase, 3‐epimerase, and phosphotransferase, which are critical to activation and deactivation of molting hormones in insects.
Fatty chain compositon of ether and ester glycerophospholipids in the Japanese oysterCrassostrea gigas (Thunberg)
Authors: Koizumi Chiaki , Jeong Bo Young , Ohshima Toshiaki 
Published: November 2006

AbstractThe fatty chain compositions of 1‐O‐alk‐1′‐enyl‐2‐acyl, 1‐0‐alkyl‐2‐acyl, and 1,2‐diacyl glycerophospholipids of the Japanese oysterCrassostrea gigas (Thunberg) were investigated. Major fatty chains in thesn‐1 position of 1‐alk‐1′‐enyl‐2‐acyl ethanolamine phospholipids (EPL) were 18∶0 (64.7%) and 20∶1 (11.1%). Majorsn‐1 chains of alkenylacyl choline phospholipids (CPL) were 18∶0 (63.3%) and 16∶0 (22.2%). In the case of 1‐alkyl‐2‐acyl EPL, the predominant fatty chains in thesn‐1 position were 18∶0 (51.5%), 16∶0 (16.0%) and 20∶1 (12.5%); in the case of 1‐alkyl‐2‐acyl CPL, the majorsn‐1 chains were 16∶0 (44.0%) and 14∶0 (23.4%). Saturated fatty chains were predominant in both EPL and CPL. Prominent fatty acids in thesn‐2 position of the alkenylacyl EPL were 22∶6n−3 (29.0%), 20∶5n−3 (19.0%) and 22∶2 NMID (non‐methylene interrupted dienes, 16.6%) contributing to about 65% of the total fatty acids, while alkenylacyl CPL was rich in the saturated acids 16∶0 (32.0%) and 18∶0 (9.2%). In the alkylacyl EPL, 16∶0, 18∶1n−9, 18∶0 and 16∶1n−7 were prominentsn‐2 fatty acids and accounted for 30.6%, 10.0%, 9.8%, and 8.3%, respectively. Polyunsaturated fatty acids were detected, but were present at extremely low percentages. Majorsn‐2 fatty acids in alkylacyl CPL were 16∶0 (25.4%), 22∶6n−3 (16.0%) and 20∶5n−3 (8.4%). The major fatty acids of diacyl EPL were 20∶5n−3 (22.3%), 16∶0 (17.9%), and 18∶0 (16.1%), and those of diacyl CPL were 16∶0 (30.4%), 20∶5n−3 (17.6%) and 18∶1n−7 (7.4%).
Enantiomer separations of mixtures of monoacylglycerol derivatives by HPLC on a chiral column
Authors: Takagi Toru , Ando Yasuhiro 
Published: November 2006

AbstractHigh‐performance liquid chromatographic separations of monoacylglycerol enantiomeric mixtures as their di‐3,5‐dinitrophenylurethane derivatives were carried out on a chiral stationary phase, N‐(R)‐1‐(α‐naphthyl)ethylaminocarbonyl‐(S)‐valine bonded to silica gel. The conditions for the quantitative analysis ofsn‐1 andsn‐3 enantiomeric mixtures of six saturated 1‐monoacylglycerols having consecutive even carbon numbers and ofsn‐1 andsn‐3 enantiomeric mixtures of 1‐stearoyl‐, 1‐oleoyl‐, 1‐linoleoyl‐, and 1‐linolenoyl‐glycerols were obtained. The linear relationships of logarithmic retention volumes against the number of carbons and olefinic bonds for the enantiomer homologous series are discussed, and a new concept of enantiomer separation is presented.