Diacylglycerol acyltransferase in maturing sunflower seeds

2000 ◽  
Vol 28 (6) ◽  
pp. 689-692 ◽  
Author(s):  
S. Triki ◽  
J. Ben Hamida ◽  
P. Mazliak
Keyword(s):  
Enzyme Inhibition ◽  
Microsomal Fraction ◽  
Specific Activity ◽  
Diacylglycerol Acyltransferase ◽  
Subcellular Fractions ◽  
Tween 20 ◽  
Differential Centrifugation ◽  
Sunflower Seeds ◽  
Triton X

Developing sunflower seeds exhibit a high diacylglycerol acyltransferase (DAGAT, EC 2.3.1.20) activity. The distribution of the enzyme has been studied in subcellular fractions prepared by differential centrifugation of seed homogenate. Its activity was characterized using [1-14C]oleoyl-CoA and diolein dispersed in Tween 20. Some properties of the microsomal fraction of DAGAT were investigated. Hyperbolic kinetics were observed, the apparent Km was 60 μM and the specific activity of the reaction 15 pmol/min/mg of protein. Addition of BSA (0.1%) stimulated oleate incorporation, which was not dependent on the presence of exogenous diacylglycerol. Detergents which might solubilize DAGAT, Triton X-100 and CHAPS, were tested for enzyme inhibition, and CHAPS was found to be the least denaturing.

scholarly journals The effect of phenobarbital on the submicrosomal distribution of uridine diphosphate glucuronyltransferase from rat liver

1970 ◽  
Vol 117 (2) ◽  
pp. 319-324 ◽  
Author(s):  
G. J. Mulder
Keyword(s):  
Enzyme Activity ◽  
Density Gradient ◽  
Rat Liver ◽  
Microsomal Fraction ◽  
Specific Activity ◽  
Sucrose Density Gradient ◽  
Male Rats ◽  
Uridine Diphosphate ◽  
Triton X

1. The detergent Triton X-100 activates UDP glucuronyltransferase from rat liver in vitro six- to seven-fold with p-nitrophenol as substrate. The enzyme activity when measured in the presence of Triton X-100 is increased significantly by pretreatment of male rats with phenobarbital for 4 days (90mg/kg each day intraperitoneally). If no Triton X-100 is applied in vitro such an increase could not be shown. In all further experiments the enzyme activity was measured after activation by Triton X-100. 2. The Km of the enzyme for the substrate p-nitrophenol does not change on phenobarbital pretreatment. 3. When the microsomal fraction from the liver of untreated rats is subfractionated on a sucrose density gradient, 47% of the enzyme activity is recovered in the rough-surfaced microsomal fraction, which also has a higher specific activity than the smooth-surfaced fraction. 4. Of the increase in activity after the phenobarbital pretreatment 50% occurs in the smooth-surfaced fraction, 19% in the rough-surfaced fraction and 31% in the fraction located between the smooth- and rough-surfaced microsomal fractions on the sucrose density gradient. 5. The latency of the enzyme in vitro, as shown by the effect of the detergent Triton X-100, is discussed in relation to the proposed heterogeneity of UDP glucuronyltransferase.

scholarly journals ISOLATION OF TWO DISTINCT CLASSES OF POLYSOMES FROM A NUCLEAR FRACTION OF RAT LIVER

1968 ◽  
Vol 37 (1) ◽  
pp. 163-181 ◽  
Author(s):  
Paul D. Sadowski ◽  
Janet Alcock Howden
Keyword(s):  
Outer Membrane ◽  
Rat Liver ◽  
Orotic Acid ◽  
Specific Activity ◽  
Nuclear Fraction ◽  
Differential Centrifugation ◽  
Rat Liver Nuclei ◽  
Liver Nuclei ◽  
Triton X

Isolated rat liver nuclei were washed with Triton-X-100 in the presence of liver cell sap. This treatment liberated a fraction of polysomes which were isolated by differential centrifugation and were designated "outer membrane polysomes." The outer membrane polysomes synthesized protein in vivo. Shortly after injection of orotic acid-14C, the RNA of outer membrane polysomes had a higher specific activity than that of cytoplasmic polysomes. It was postulated that outer membrane polysomes may be an intermediate in the transfer of newly synthesized RNA from the nucleus to the cytoplasm. In other experiments, Triton-washed rat liver nuclei were lysed in the presence of deoxycholate and deoxyribonuclease. A ribonucleoprotein fraction was isolated from the lysate by differential centrifugation. This fraction contained "intranuclear ribosomes," which sedimented like partially degraded polysomes in sucrose gradients. This degradation could be partially prevented if intranuclear ribosomes were purified by sedimentation through heavy sucrose. The resulting pellets were termed "intranuclear polysomes" because they contained some undergraded polysomes. Intranuclear polysomes were highly radioactive after a brief pulse with orotic acid-14C, but did not appear to synthesize protein rapidly in vivo. Intranuclear polysomes may represent the initial stage of assembly of polyribosomes in the nucleus.

CONVERSION OF ANDROST-4-ENE-3,17-DIONE-4-14C TO OESTROGENS BY SUBCELLULAR FRACTIONS OF THE HUMAN CORPUS LUTEUM OF THE NORMAL CYCLE

1967 ◽  
Vol 56 (2) ◽  
pp. 225-230 ◽  
Author(s):  
Rosalinda B. Arceo ◽  
Kenneth J. Ryan
Keyword(s):  
Subcellular Localization ◽  
Corpus Luteum ◽  
Paper Chromatography ◽  
Specific Activity ◽  
Subcellular Fractions ◽  
Corpora Lutea ◽  
Differential Centrifugation ◽  
Normal Cycle ◽  
Generating System ◽  
Human Corpus Luteum

ABSTRACT The subcellular localization of the aromatizing enzymes from four human corpora lutea was investigated. Subcellular fractions were prepared by differential centrifugation, and incubations of each fraction were carried out with androst-4-ene-3,17-dione-4-14C and a TPNH generating system. Oestrogen metabolites were characterized by phenolic separation, repeated paper chromatography, incubation with freshly prepared placental 17β-ol dehydrogenase, methylation and recrystallization to constant specific activity. The experimental results indicate that the aromatizing enzymes were localized mainly in the microsomal fractions of homogenates of human corpora lutea.

TESTOSTERONE METABOLISM IN SUBCELLULAR FRACTIONS OF RAT PROSTATE

1973 ◽  
Vol 73 (3) ◽  
pp. 585-598 ◽  
Author(s):  
Kaoru Nozu ◽  
Bun-ichi Tamaoki
Keyword(s):  
Microsomal Fraction ◽  
Specific Activity ◽  
Hydroxysteroid Dehydrogenase ◽  
Inhibitory Effect ◽  
Subcellular Fractions ◽  
Hydrogenase Activity ◽  
Nuclear Fraction ◽  
Cytosol Fraction ◽  
Testosterone Metabolism ◽  
Major Activity

ABSTRACT Homogenates of rat ventral prostates were fractionated into the nuclear (purified from the precipitate at 800× g), mitochondrial (precipitate at 1000–6000 ×g), microsomal (precipitate at 10 000–105 000× g) and cytosol (supernatant fluid at 105 000 × g) fractions, which were morphologically identified under an electron-microscope. Among the subcellular fractions, the highest specific activity of Δ4-5α-hydrogenase was localized in the nuclear and microsomal fractions, while 3α-hydroxysteroid dehydrogenase (E. C. 1. 1. 1.50) activity was concentrated exclusively in the cytosol fraction. By addition of the cytosol fraction, the Δ4-5α-hydrogenase activity in the microsomal fraction was markedly reduced, whereas the activity in the nuclear fraction was scarcely inhibited. By heating the cytosol fraction at 100°C for 20 min, its inhibitory effect was significantly diminished. The inhibitory principle in the cytosol fraction against the Δ4-5α-hydrogenase was mostly concentrated in the precipitate at 0–60% saturation of ammonium sulphate, while the major activity of the 3α-hydroxysteroid dehydrogenase was localized in the precipitate at 40–100% saturation of the salt. According to the enzyme kinetics, the cytosol 0–40 % fraction showed the competitive type of inhibition with the Δ4-5α-hydrogenase activity in the microsomal fraction for testosterone.

scholarly journals The biosynthesis of sulphogalactosyldiacylglycerol of rat brain in vitro

1977 ◽  
Vol 166 (3) ◽  
pp. 429-435 ◽  
Author(s):  
G. Subba Rao ◽  
Leonard N. Norcia ◽  
Joanne Pieringer ◽  
Ronald A. Pieringer
Keyword(s):  
Enzyme Activity ◽  
Rat Brain ◽  
Enzyme Preparation ◽  
Microsomal Fraction ◽  
Inhibitory Effect ◽  
Subcellular Fractions ◽  
Triton X ◽  
Derivatives Of

Triton X-100 extracts of rat brain microsomal fraction catalyse the formation of sulphogalactosyldiacylglycerol from galactosyldiacylglycerol and adenosine 3′-phosphate 5′-sulphatophosphate. Of the various subcellular fractions of brain assayed, the microsomal fraction contained most (79%) of the adenosine 3′-phosphate 5′-sulphatophosphate–galactosyldiacylglycerol sulphotransferase activity. The enzyme activity was stimulated by Triton X-100 and showed linearity with increasing time, concentrations of enzyme and added substrates. ATP and KF prolonged the linearity of the activity with time, but ATP had an overall inhibitory effect on the sulphotransferase. Both ATP and KF inhibit the degradation of adenosine 3′-phosphate 5′-sulphatophosphate, which probably causes the increased linearity of the sulphotransferase reaction with time. The enzyme preparation did not catalyse the transfer of sulphate from adenosine 3′-phosphate 5′-sulphatophosphate to either cholesterol or galabiosyldiacylglycerol (galactosylgalactosyldiacylglycerol). Significant differences between the formation of sulphogalactosyldiacylglycerol and cerebroside sulphate catalysed by the same enzyme preparation were noted. ATP and Mg2+ strongly inhibit the formation of sulphogalactosyldiacylglycerol but equally strongly stimulate the synthesis of cerebroside sulphate. The apparent Km for galactosyldiacylglycerol is 200μm, and that for cerebroside is 45μm. Galactosyldiacylglycerol and cerebroside are mutually inhibitory toward the synthesis of sulphated derivatives of each. These data do not necessarily lead to the conclusion that two sulphotransferases are present, but they do indicate a possible means of controlling the synthesis of these two sulpholipids.

INCORPORATION OF RADIOACTIVE PRECURSORS INTO THE MEMBRANE AND CONTENTS OF THE NEUROSECRETORY GRANULES OF THE RAT NEUROHYPOPHYSIS AS A METHOD OF STUDYING THEIR FATE

1976 ◽  
Vol 68 (1) ◽  
pp. 95-108 ◽  
Author(s):  
R. W. SWANN ◽  
B. T. PICKERING
Keyword(s):  
Membrane Fraction ◽  
Microsomal Fraction ◽  
Subcellular Fractions ◽  
Secretory Product ◽  
Neurosecretory Granules ◽  
Differential Centrifugation ◽  
Nacl Solution ◽  
Neurohypophysial Hormones ◽  
Intracisternal Injection ◽  
Membrane Bound

SUMMARY Rat neural lobes have been separated into subcellular fractions by differential centrifugation at various times after an intracisternal injection of [35S]cysteine or [3H]choline. Both isotopes led to a rise and fall in the radioactivity of neurosecretory granules (NSG) which paralleled that found previously for the neurohypophysial hormones and the neurophysins. While the radioactivity of the NSGs resulting from [35S]cysteine injection was predominantly associated with granular contents, [3H]choline injections led to a preferential labelling of the granular membrane. There was no indication of a sequential movement of radioactivity from the NSG-membrane fraction into the microsomal fraction (containing the so-called small vesicles) which might be expected if granular membrane were recaptured as small vesicles after release of secretory product by exocytosis. When release was stimulated in injected animals by giving them 2% NaCl solution to drink, 35S disappeared from the gland as expected, but 3H was retained and, moreover, appeared in the NSG-membrane fraction; results compatible with membrane conservation occurring by recapture of large vesicles. There was an indication that some of the neurophysin in the NSG was membrane-bound and that this too was retained after release of the granular contents.

scholarly journals SUBCELLULAR LOCALIZATION OF RAT BRAIN ESTERASES

1966 ◽  
Vol 14 (6) ◽  
pp. 455-472 ◽  
Author(s):  
JOSEPH BERNSOHN ◽  
KEVIN D. BARRON ◽  
PAUL F. DOOLIN ◽  
ADELINE R. HESS ◽  
MARJORIE T. HEDRICK
Keyword(s):  
Rat Brain ◽  
Specific Activity ◽  
Subcellular Fractions ◽  
Synaptic Membranes ◽  
Nonspecific Esterase ◽  
Starch Gel Electrophoresis ◽  
Quantitative Chemical Analysis ◽  
Electron Microscopic ◽  
E 600 ◽  
Triton X

The localization and properties of soluble and bound esterases of subcellular fractions of rat brain have been investigated. Bound esterases were extracted with 1% Triton X-100 and separated by starch gel electrophoresis. By these means a molecular population of isoenzymes was demonstrable that was quantitatively different from the isoenzyme population of the watersoluble esterase activity. The highest specific activity for α-naphthyl acetate hydrolysis was contained in the microsomal fraction and could be extracted by Triton. In contradistinction to whole brain and to other subcellular fractions, microsomes contained a molecular population of esterase isozymes which was qualitatively distinct from that of water extracts in that the fast moving A-type esterases were absent. In addition, there was present a heavy concentration of slow movinig B-esterase. Acetylcholinesterase could also be extracted from this fraction by Triton, migrated with B-esterase and actively hydrolyzed αnaphthyl acetate. Combined electron microscopic and quantitative chemical analysis of the subcellular fractions suggested that some bound nonspecific esterase may be localized in sub-synaptic membranes. The pI50 values for E 600 of the soluble and insoluble, Triton X-100-extracted and Triton X-100-insoluble esterases are, respectively, 5.3, 7.5, 7.5 and 7.4. It is noted that these results may be determined in part by the participation of acetylcholinesterase in hydrolysis of the substrate. Mitochondria are virtually devoid of esteratic activity. C-type esterase (CMB-activated, E 600-resistant) occurred in both the bound and soluble state. A-, B- and C-type esterases exist in both bound and soluble forms and their chemical properties appear to be independent of their site of localization. Histochemical studies indicate that the B-type esterase is localized predominantly to cytoplasm of neurons and to neuropil. A-esterase is localized to droplets (presumed lysosomes) of neurons and other cell types, e.g., pericytes. The histochemical localization of C-esterase could not be determined.

Secretagogue-induced changes in subcellular Ca2+ distribution in isolated pancreatic acini

1981 ◽  
Vol 240 (2) ◽  
pp. G130-G140
Author(s):  
R. L. Dormer ◽  
J. A. Williams
Keyword(s):  
Atomic Absorption Spectrometry ◽  
High Speed ◽  
Microsomal Fraction ◽  
Absorption Spectrometry ◽  
Subcellular Fractionation ◽  
Differential Centrifugation ◽  
Zymogen Granules ◽  
Pancreatic Acini ◽  
Induced Changes ◽  
Stimulation Of

In a prior study, we demonstrated that pancreatic secretagogues increased both the uptake into and washout of 45Ca2+ from isolated mouse pancreatic acini. The net result of these processes was an initial fall in total acinar cell Ca2+ content. In the present study, we have employed subcellular fractionation of acini under conditions that minimized posthomogenization redistribution of Ca2+ in order to localize those organelles involved in intracellular Ca2+ fluxes. Homogenization and differential centrifugation of acini, preloaded with 45Ca2+ and subjected to a period of washout, showed that carbachol induced an increased loss of 45Ca2+ from all fractions isolated. The high-speed microsomal fraction lost 45Ca2+ to a greater extent than did whole acini; measurement of total Ca2+ by atomic absorption spectrometry showed a net loss of Ca2+ from this fraction. Purification of the lower-speed fractions indicated that carbachol increased 45Ca2+ exchange with both zymogen granules and mitochondria, but net Ca2+ levels in these organelles were unchanged. It was concluded that stimulation of pancreatic acini by carbachol results in the release of calcium from a microsomal compartment leading to a rise in cytoplasmic Ca2+, increased exchange with granule and mitochondrial Ca2+, and increased efflux of Ca2+ from the cell.

The efficiency of various detergents for extraction and stabilization of acetylcholinesterase from bovine erythrocytes

1987 ◽  
Vol 65 (1) ◽  
pp. 8-18 ◽  
Author(s):  
Rex K. M. Wong ◽  
Christine P. Nichol ◽  
M. Chandra Sekar ◽  
Basil D. Roufogalis
Keyword(s):  
Chain Length ◽  
Membrane Lipids ◽  
Acetylcholinesterase Activity ◽  
Exchange Chromatography ◽  
Erythrocyte Membranes ◽  
Tween 20 ◽  
Bovine Erythrocyte ◽  
Critical Micelle Concentrations ◽  
Triton X ◽  
Nonionic Detergents

The efficiency of several nonionic detergents and a homologous series of zwitterionic detergents for the extraction of acetylcholinesterase (EC 3.1.1.7) from bovine erythrocyte membranes was examined. Of the nonionic detergents examined, the polyoxyethylene-based Tweens were the least effective solubilizing agents. Within this series, increasing the length of the saturated fatty acid chain progressively decreased the efficiency of enzyme recovery, while unsaturation in the side chain reversed this trend. In the Lubrol detergents, where the chain length of the alcohol group is variable, an increase in the length of the polyoxyethylene glycol group decreased the recovery of acetylcholinesterase in the solubilized state, without affecting the efficiency of extraction of total erythrocyte protein. As with the other nonionic detergents examined, Triton X-100 and octy1 β-D-glucoside were maximally effective in solubilizing acetylcholinesterase activity at concentrations greater than their respective critical micelle concentrations. In the sulfobetaine (N-alkyldimethylaminopropane sulphonate) zwitterionic detergent series, the longer alkyl chain zwittergents Z 316 and Z 314 were more efficient than the shorter chain length members of the series (Z 310 and Z 312). In contrast to the higher chain length compounds, short chain analogs were maximally effective at or below their critical micelle concentrations. After purification by ion-exchange chromatography and affinity chromatography, the enzyme extracted with the various detergents gave sedimentation coefficients between 6.8S and 7.6S, consistent with a dimeric structure. Acetylcholinesterase could also be efficiently released by 0.2 mM EDTA or 0.5 M NaCl from bovine erythrocyte membranes previously depleted of 70–80% of the membrane lipids by butanol. Nonlinear Arrhenius plots of enzyme activity were found whether acetylcholinesterase was solubilized with Tween 20, Lubrol PX, or Triton X-100. The present work confirms that bovine erythrocyte acetylcholinesterase requires detergents to solubilize it from membranes and that its activity depends on the structure of the amphiphiles used to solubilize the enzyme.

scholarly journals Mucin biosynthesis. Properties of a bovine tracheal mucin β-6-N-acetylglucosaminyltransferase

1985 ◽  
Vol 227 (2) ◽  
pp. 405-412 ◽  
Author(s):  
P W Cheng ◽  
W E Wingert ◽  
M R Little ◽  
R Wei
Keyword(s):  
Enzyme Activity ◽  
Freezing Point ◽  
Cetylpyridinium Chloride ◽  
Sodium Dodecyl ◽  
Sodium Deoxycholate ◽  
Gas Chromatography Mass Spectrometry ◽  
Tween 20 ◽  
Group A ◽  
Michaelis Constants ◽  
Triton X

We have characterized a bovine tracheal mucin beta-6-N-acetylglucosaminyltransferase that catalyses the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to the C-6 of the N-acetylgalactosamine residue of galactosyl-β 1→3-N-acetylgalactosamine. Optimal enzyme activity was obtained between pH 7.5-8.5, at 5mM-MnCl2, and at 0.06-0.08% (v/v) Triton X-100 (or Nonidet P-40), or 0.5-5.0% (v/v) Tween 20. Ba2+, Mg2+ and Ca2+ could partially replace Mn2+, but Co2+, Fe2+, Cd2+ and Zn2+ could not. Sodium dodecyl sulphate, cetylpyridinium chloride, sodium deoxycholate, octyl beta-D-glucoside, digitonin and alkyl alcohols were less effective in enhancing enzyme activity, and dimethyl sulphoxide was ineffective. The apparent Michaelis constants were 1.25 mM for UDP-N-acetylglucosamine, 0.94-3.34 mM for freezing-point-depressing glycoprotein and 0.19 mM for periodate-treated blood-group-A porcine submaxillary mucin. Asialo ovine submaxillary mucin could not serve as the glycosyl acceptor. The structure of the 14C-labelled oligosaccharide obtained by alkaline-borohydride treatment of the product was identified as Gal beta 1→3(Glc-NAc beta 1→6)N-acetylgalactosaminitol by beta-hexosaminidase treatment, gas chromatography-mass spectrometry and 1H-n.m.r. (270 MHz) analysis. The enzyme is important in the regulation of mucin oligosaccharide biosynthesis.

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