Occurrence and Biosynthesis of Ceramide Phosphorylethanolamine in Chicken and Rat Liver

1972 ◽  
Vol 50 (2) ◽  
pp. 166-173 ◽  
Author(s):  
Bernd A. Muehlenberg ◽  
Michael Sribney ◽  
Marilyn Kemp Duffe
Keyword(s):  
Rat Liver ◽  
Reaction Rate ◽  
Hydroxyl Group ◽  
Transferase Activity ◽  
Manganese Ions ◽  
Sulfhydryl Reagents ◽  
Ph Optimum ◽  
Optimal Activity ◽  
Threo Isomer ◽  
Do So

Ceramide phosphorylethanolamine has been found to occur in chicken and rat liver. An enzyme (CDP-ethanolamine:ceramide ethanolaminephosphotransferase) has been found in a number of tissues which catalyzes the biosynthesis of this lipid. The enzyme catalyzes the transfer of the phosphorylethanolamine moiety of CDP-ethanolamine to the free primary hydroxyl group of a ceramide (N-acylsphingosine). The chicken liver enzyme requires 0.010 M manganese ions for optimal activity and has a pH optimum of 7.7. The Km for the substrate N-octanoyl-threo-sphingosine was found to be 2.5 × 10−4 M. A study of the effect of increasing CDP-ethanolamine concentration on the reaction rate indicates from sigmoid kinetics that the coenzyme modulates and possibly regulates PE-ceramide transferase activity. The enzyme differs from sphingomyelin synthetase (CDP-choline:ceramide cholinephosphotransferase) in that it will only utilize the unnatural threo isomer of N-acylsphingosines (threo-ceramides) as acceptors for the phosphorylethanolamine moiety of CDP-ethanolamine. Sphingomyelin synthetase has been shown to utilize erythro-ceramides the presence of sulfhydryl reagents (Sribney, M.: Can. J. Biochem. 49, 306 (1971)); the enzyme catalyzing the biosynthesis of ceramide phosphorylethanolamine, however, does not do so, even in the presence of a variety of sulfhydryl reagents tested.

UDP-Glucose: Anthocyanidin/FIavonol 3-O-Glucosyltransferase in Enzyme Preparation from Flower Extracts of Genetically Defined Lines of Matthiola incana R. Br.

1986 ◽  
Vol 41 (7-8) ◽  
pp. 699-706 ◽  
Author(s):  
M. Teusch ◽  
G. Forkmann ◽  
W. Seyffert
Keyword(s):  
Enzyme Activity ◽  
Structural Gene ◽  
Enzyme Preparation ◽  
Reaction Rate ◽  
Flower Colour ◽  
Hydroxyl Group ◽  
Anthocyanin Synthesis ◽  
Ph Optimum ◽  
Matthiola Incana ◽  
Highly Active

Abstract In flower extracts of Matthiola incana an enzyme catalyzing the transfer of glucose from UDP- glucose to the hydroxyl group at 3-position of anthocyanidins and flavonols was demonstrated. The pH-optimum of this reaction is at pH 8.5 for pelargonidin and pH 9.5 for quercetin as substrate. The reaction is inhibited by both substrates above 10 nmol per assay. The enzyme is highly active, within 30 sec 3 nmol of 3-glucosides were formed. At 30 °C the enzyme is stable for hours and at -20 °C months. Besides UDP-glucose, TDP-glucose is a suitable glucosyl-donor, but with a reduced (70%) reaction rate. Enzyme activity is clearly inhibited by Fe2+ and Cu2+ ions, and by diethylpyrocarbonate. Acyanic or pale coloured mutants of several genes interfering with anthocyanin synthesis after dihydroflavonol formation show a more or less drastically reduced enzyme activity (5-40%). But none of these genes can be regarded as the structural gene for the 3-glucosyltransferase. The influence of these genes on enzyme activity and flower colour is dis­cussed.

Distribution of Dipeptidase Activity between Lysosomes and Soluble Fraction of Rat Liver

1975 ◽  
Vol 53 (5) ◽  
pp. 502-508 ◽  
Author(s):  
Steve L. Taylor ◽  
Al L. Tappel
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Soluble Fraction ◽  
Bimodal Distribution ◽  
Sulfhydryl Reagents ◽  
Ph Optimum ◽  
Triton Wr 1339 ◽  
Dipeptidase Activity ◽  
Soluble Fractions

Dipeptidase activity toward Arg-Phe, Arg-Gly, and Trp-Leu exhibited bimodal distribution in the lysosomal and soluble fractions of rat liver. The majority (50–70%) of the dipeptidase activity was present in the soluble fraction. Some evidence for a plasma membrane dipeptidase, which hydrolyzes Trp-Leu but not Arg-Phe or Arg-Gly, also was found. The lysosomal dipeptidase activity had a pH optimum of 6.0–7.0, and was activated by sulfhydryl reagents. Lysosomal localization for some of the dipeptidase activity was established with Triton WR-1339 fractionation and latency experiments.

scholarly journals Sequential deiodination of thyroxine in rat liver homogenate

1978 ◽  
Vol 174 (1) ◽  
pp. 221-229 ◽  
Author(s):  
T J Visser ◽  
D Fekkes ◽  
R Docter ◽  
G Hennemann
Keyword(s):  
Rat Liver ◽  
Reaction Rate ◽  
Liver Homogenate ◽  
Ph Optimum ◽  
High Reaction ◽  
High Reaction Rate

Rat liver homogenate was incubated at 37 degrees C with thyroxine, 3,3′,5-tri-iodothyronine, 3,3′,5′-tri-iodothyronine or 3,3′-di-iodothyronine. The degradation or accumulation of these compounds was measured by specific radioimmunoassays. (1) Production of 3,3′,5-tri-iodothyronine from thyroxine was highest at pH 6.0–6.5 and was markedly stimulated by the addition of dithiothreitol and effectively inhibited in the presence of 6-propyl-2-thiouracil. (2) Accumulation of 3,3′,5′-tri-iodothyronine on incubation of thyroxine with homogenate was only observed above pH 8.5. Otherwise the product was converted into 3,3′-di-iodothyronine too rapidly to allow its measurement. By measuring 3,3′-di-iodothyronine it was deduced that 5-deiodination of thyroxine was most effective at approx. pH 8.0. Dithiothreitol powerfully stimulated this reaction and 6-propyl-2-thiouracil strongly inhibited. (3) Monodeiodination of the tyrosine ring of 3,3′,5-tri-iodothyronine was the slowest reaction, was optimal at pH 8.0 and was less affected by dithiothreitol and 6-propyl-2-thiouracil than the above reactions. (4) 5′-Deiodination of 3,3′,5′-tri-iodothyronine was extremely rapid, with a pH optimum probably at about 6.5. Owing to the high reaction rate under the conditions used it was not possible to assess the effects of dithiothreitol and 6-propyl-2-thiouracil.

scholarly journals The distribution, induction and isoenzyme profile of glutathione S-transferase and glutathione peroxidase in isolated rat liver parenchymal, Kupffer and endothelial cells

1989 ◽  
Vol 264 (3) ◽  
pp. 737-744 ◽  
Author(s):  
P Steinberg ◽  
H Schramm ◽  
L Schladt ◽  
L W Robertson ◽  
H Thomas ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Glutathione Peroxidase ◽  
Rat Liver ◽  
Peroxidase Activity ◽  
Cell Types ◽  
Transferase Activity ◽  
Glutathione Peroxidase Activity ◽  
Glutathione S Transferase ◽  
Liver Parenchymal ◽  
Parenchymal Cells

The distribution and inducibility of cytosolic glutathione S-transferase (EC 2.5.1.18) and glutathione peroxidase (EC 1.11.1.19) activities in rat liver parenchymal, Kupffer and endothelial cells were studied. In untreated rats glutathione S-transferase activity with 1-chloro-2,4-dinitrobenzene and 4-hydroxynon-2-trans-enal as substrates was 1.7-2.2-fold higher in parenchymal cells than in Kupffer and endothelial cells, whereas total, selenium-dependent and non-selenium-dependent glutathione peroxidase activities were similar in all three cell types. Glutathione S-transferase isoenzymes in parenchymal and non-parenchymal cells isolated from untreated rats were separated by chromatofocusing in an f.p.l.c. system: all glutathione S-transferase isoenzymes observed in the sinusoidal lining cells were also detected in the parenchymal cells, whereas Kupffer and endothelial cells lacked several glutathione S-transferase isoenzymes present in parenchymal cells. At 5 days after administration of Arocolor 1254 glutathione S-transferase activity was only enhanced in parenchymal cells; furthermore, selenium-dependent glutathione peroxidase activity decreased in parenchymal and non-parenchymal cells. At 13 days after a single injection of Aroclor 1254 a strong induction of glutathione S-transferase had taken place in all three cell types, whereas selenium-dependent glutathione peroxidase activity remained unchanged (endothelial cells) or was depressed (parenchymal and Kupffer cells). Hence these results clearly establish that glutathione S-transferase and glutathione peroxidase are differentially regulated in rat liver parenchymal as well as non-parenchymal cells. The presence of glutathione peroxidase and several glutathione S-transferase isoenzymes capable of detoxifying a variety of compounds in Kupffer and endothelial cells might be crucial to protect the liver from damage by potentially hepatotoxic substances.

Biosynthesis of the Diguanosine Nucleotides. I. Purification and Properties of an Enzyme from Yolk Platelets of Brine Shrimp Embryos

1974 ◽  
Vol 52 (3) ◽  
pp. 231-240 ◽  
Author(s):  
A. H. Warner ◽  
P. C. Beers ◽  
F. L. Huang
Keyword(s):  
Molecular Weight ◽  
Brine Shrimp ◽  
Artemia Salina ◽  
Temperature Optimum ◽  
Small Molecular Weight ◽  
Ph Optimum ◽  
Optimal Activity ◽  
Purification And Properties

An enzyme that catalyzes the synthesis of P1P4-diguanosine 5′-tetraphosphate (Gp4G) has been isolated and purified from yolk platelets of encysted embryos of the brine shrimp, Artemia salina. The enzyme GTP:GTP guanylyltransferase (Gp4G synthetase) utilizes GTP as substrate, has a pH optimum of 5.9–6.0, a temperature optimum of 40–42 °C, and requires Mg2+ and dithiothreitol for optimal activity. The synthesis of Gp4G is inhibited markedly by pyrophosphate, whereas orthophosphate has no effect on the reaction. In the presence of GDP the enzyme also catalyzes the synthesis of P1,P3-diguanosine 5′-triphosphate (Gp3G), but the rate of synthesis is low compared with Gp4G synthesis and dependent upon other small molecular weight components of yolk platelets.

Acetylsalicylic acid hydrolase of gastric mucosa.

1978 ◽  
Vol 234 (6) ◽  
pp. E606
Author(s):  
J G Spenney
Keyword(s):  
Gastric Mucosa ◽  
Enzymatic Activity ◽  
Acetylsalicylic Acid ◽  
Sodium Dodecyl ◽  
Sodium Cholate ◽  
Acid Hydrolase ◽  
Sulfhydryl Reagents ◽  
Ph Optimum ◽  
Diisopropyl Fluorophosphate

Acetylsalicylic acid hydrolase activity of rabbit fundic gastric mucosa has been isolated from the soluble 100,000 X g supernate. The enzymatic activity was partially purified by ammonium sulfate precipitation. The Km for acetylsalicylate was 2 mM and pH optimum was 8.6. The activity was insensitive to ionic strength, slightly inhibited by inclusion of 100 mM Cl-, and demonstrated no requirement for Ca2+ or Mg2+. Acetylsalicylic acid esterase was markedly inhibited by sodium cholate and sodium dodecyl sulfate. The enzyme was insensitive to sulfhydryl reagents with the exception of p-chloromercuribenzenesulfonic acid, which markedly inhibited the enzyme. Diisopropyl fluorophosphate (DFP) inhibited enzymatic activity with a Ki of 9 X 10(-9)M. Eserine was also inhibitory with a Ki of 0.25 mM. Inhibition by DFP at low concentration and by eserine at millimolar concentrations suggests that this enzyme is related to the group of aliphatic esterases. Identification of potent inhibitors will enable studies to define the role of this enzyme with the use of experimental preparations in which systemic toxicity can be avoided.

scholarly journals Optimisation of pH, Temperature and Carbon Nitrogen Ratio for the Degradation of m-Chlorophenol by Pseudomonas putida CP1

1970 ◽  
Vol 23 (2) ◽  
pp. 159-161 ◽  
Author(s):  
ANM Fakhruddin ◽  
M Alamgir Hossain
Keyword(s):  
Chemical Oxygen Demand ◽  
Pseudomonas Putida ◽  
C:N Ratio ◽  
Oxygen Demand ◽  
Hydroxyl Group ◽  
Ph Optimum ◽  
Effective Removal ◽  
Carbon Nitrogen Ratio ◽  
Chlorine Substituent ◽  
Nitrogen Ratio

Aromatic pollutants like m-chlorophenol is toxic to the environment and chlorophenol containing a metachlorine are more persistent under aerobic conditions than compounds lacking a chlorine substituent in positions meta to hydroxyl group. Therefore, it should be removed effectively from the environment. In order to increase the degradative activity, the optimum conditions for m-chlorophenol degradation by Pseudomonas putida CP1, some physicochemical conditions like pH, temperature and carbon nitrogen ratio for the growth and degradation of most persistent monochlorophenol, m-chlorophenol by the organism was optimised. The pH optimum for m-chlorophenol degradation by the bacterium was between pH 6.5 and 7.0 and the temperature optimum was 30°C for removal activity. Carbon : nitrogen (C:N) ratio of 3:1 was found best for effective removal of chemical oxygen demand (COD) and m-chlorophenol by the bacterium. Keywords: m-Chlorophenol degradation, Pseudomonas putida CP1, Chemical oxygen demand (COD)DOI: http://dx.doi.org/10.3329/bjm.v23i2.884  Bangladesh J Microbiol, Volume 23, Number 2, December 2006, pp 159-161

STUDIES ON SOLUBILIZED ADENYLATE KINASE FROM MITOCHONDRIA

1966 ◽  
Vol 44 (11) ◽  
pp. 1469-1475 ◽  
Author(s):  
Marjorie A. Brewster ◽  
Ezzat S. Younathan
Keyword(s):  
Activation Energy ◽  
Rat Liver ◽  
Adenylate Kinase ◽  
Divalent Cations ◽  
Metabolic Function ◽  
Kcal Mole ◽  
Temperature Optimum ◽  
Ph Optimum ◽  
Sensitive Method

Adenylate kinase from mitochondria of rat liver was made soluble by sonication. The enzyme had a pH optimum of 8.0, temperature optimum of 30°, and activation energy of 12.2 kcal/mole. It was activated by several divalent cations in the following order of efficiency: Mg++ > Co++ > Mn++ > Ca++, with an optimal Mg++: ADP ratio of 1. The apparent Km value (ADP as substrate) was found to be 1.3 mM at pH 7.4 and 30°. The activity was sensitive to phloretin and mildly activated by aurovertin. Oligomycin, 2,4-dinitrophenol, p-chloromercuribenzoate, alloxan, and phlorizin had no effect on the activity. The metabolic function and a comparison of the properties of this solubilized mitochondrial adenylate kinase with those of similar preparations from other sources are discussed in the light of these findings. During this study, a sensitive method adaptable for a large number of assays of adenylate kinase was developed, and is described in detail.

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