R Morelis

University of Lyon, Lyons, Rhône-Alpes, France

Are you R Morelis?

Claim your profile

Publications (42)85.21 Total impact

  • Monique Léon, Renée Morelis, P. Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: We have shown that the fucosyltransferase activity was located in two subcellular fractions: the microsomes and the synaptosomes. The localization of enzyme activity was identical in the young and in the adult rat brain. The values of some parameters of the microsomal enzyme (Km, optimum temperature, optimum pH) in the young and in the adult rat brain shown that the enzyme affinity for its substrate is in relation with the brain maturation.
    09/2008; 91(2):121-125.
  • Odile GATEAU, Renée MORELIS, Pierre LOUISOT
    [Show abstract] [Hide abstract]
    ABSTRACT: Biosynthesis of Dolichol Phosphate Mannose in the Mitochondrial Outer MembranePrevious studies have shown that mannose incorporation into mitochondrial glycoproteins is catalysed by a mannosyl-transferase, which is located in the mitochondrial inner membrane. It seems important to study the presence of mannosyl-transferases which are able to catalyse the transfer of mannose into other acceptors, such as polyprenic intermediates.Mouse liver mitochondria catalyse the incorporation of mannose from GDP-[14C]mannose into three products: most of the radioactivity is in a product (A) soluble in chloroform/methanol (2/1, by vol.); mannose is also incorporated into product (B) soluble in chloroform/methanol/water (10/10/3, by vol.), and into a product which is insoluble in organic solvents and trichloroacetic acid and which is a glycoprotein. We have tried to localize in mitochondria the mannosyl-transferases implicated in these reactions.Mitochondrial outer membranes were prepared by swelling purified mitochondria in phosphate buffer, and were purified on a discontinuous sucrose gradient. The purified outer membranes catalyse the incorporation of mannose from GDP-[14C]mannose in very large quantities into product A and in small quantities into product B.Different procedures (purification on silicic acid and DEAE-cellulose, hydrolytic procedures and chromatographic properties) demonstrated the identity of product A with authentic dolichol phosphate mannose.Product B is lipid-linked oligosaccharides.The biosynthesis of dolichol phosphate mannose depends on Mn2+. When ethyleneglycol bis(2-aminoethyl)N,N′-tetracetic-acid (EGTA) is added to the mixture, the reaction is inhibited. When EGTA is added to a mixture containing preformed endogenous dolichol phosphate [14C]mannose, the biosynthesis of the product stops, and the product is hydrolysed, with a concomitant apparition of lipid-linked-oligosaccharides. These results and the kinetics of the reactions suggest that dolichol phosphate mannose might be the mannosyl donor for the lipid-linked-oligosaccharides. The synthesis of dolichol phosphate mannose is reversed by the addition of GDP.The role of these products as intermediates in mitochondrial glycoprotein biosynthesis is discussed.
    European Journal of Biochemistry. 06/2008; 88(2):613 - 622.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The activity of GDPmannose:dolichyl monophosphate mannosyltransferase in inner mitochondrial membranes can be triggered by dolichyl-monophosphate incorporation mediated through phospholipids or fatty acids. The efficiency of this incorporation and the efficiency of the enzyme activity are not equivalent. Among a variety of amphiphiles which were tested, the highest mannosyltransferase activity was obtained with the mixture of lipids extracted from the outer mitochondrial membranes. The results presented here appear consistent only with a mechanism involving collisional contacts of the phospholipid vesicles and fusion with the membranes. ESR spectroscopy confirms that (a) the incorporation process is followed by solubilization of dolichyl monophosphate molecules in the lipid phase and (b) the general organization of the inner mitochondrial membranes is not perturbed by the addition of dolichyl monophosphate.
    European Journal of Biochemistry 04/1990; 188(3):547-56. · 3.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Physiological and membranous modifications induced by a 4-week ethanol administration in mouse liver plasma membrane were studied. Galactosyl- and glucosyltransferase activities were stimulated in the presence of dolichylphosphate alone or with phosphatidyl-choline. The galactosyltransferase activity was inhibited by chronic ethanol administration. These enzymes were modulated by different phospholipids. The phosphatidic acid was the most efficient activator. Ethanol provoked an inhibition of the galactosyltransferase activity whatever the phospholipid used, as well as an inhibition of the glucosyltransferase activity, chiefly in presence of phosphatidyl-inositol. The preincubation of control or treated mouse liver plasma membranes with liposomes loaded by dolichylphosphate and cholesterol greatly enhanced the enzymatic activities without removing the inhibition by ethanol treatment.
    Pharmacology Biochemistry and Behavior 02/1990; 35(1):75-84. · 2.61 Impact Factor
  • C Levrat, P Louisot, R Morelis
    [Show abstract] [Hide abstract]
    ABSTRACT: The trypsin sensitivity of the mitochondrial N-acetylglucosaminyl and mannosyltransferase activities involved in the N-glycoprotein biosynthesis through dolichol intermediates as well as the N-acetylglucosaminyl-transferase activity involved in direct N-glycosylation were examined in mitochondria and isolated outer mitochondrial membrane preparations. The trypsin action on mitochondrial membrane was checked by measuring the activities of marker enzymes (rotenone-insensitive NADH cytochrome c reductase, adenylate kinase, and monoamine oxidase). Glycosyl-transferase activities of both N-glycosylation pathways were insensitive to trypsin action and consequently were located in the outer mitochondrial membrane. Based on the activator effect of the trypsin on these enzyme activities, the results suggested two distinct orientations of their active sites. As regards the N-glycoprotein biosynthesis pathway through dolichol intermediates, the dolicholphosphoryl-mannose and dolichol-pyrophosphoryl-di-N-acetylchitobiose synthases would be oriented outside while the oligomannosyl-synthase and the oligomannosyl-transferase would be rather oriented inside in the outer membrane. The N-acetylglucosaminyl-transferase involved in the direct transfer of N-acetylglucosamine from its nucleotide donor to a proteinic acceptor would be oriented outside in the outer membrane.
    Journal of Biochemistry 08/1989; 106(1):133-8. · 3.07 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Plasma membranes were isolated from mouse liver. The purification was achieved by a modified method of Ray (1970). The validity of this fractionation procedure is controlled by measurements of specific enzymatic activities and by electron microscopy. The purified plasma membranes were found to contain galactosyltransferase which transferred galactose from UDP-galactose onto endogenous acceptors. This activity requires Mn2+ for its catalytic activity.
    Archives internationales de physiologie et de biochimie 07/1989; 97(3):221-30.
  • C Levrat, P Louisot, R Morelis
    [Show abstract] [Hide abstract]
    ABSTRACT: The liver mitochondria were submitted to a first swelling which allowed to get outer membranes. The mitoplasts obtained in these conditions were subject to a second swelling. The separation of submitochondrial membranes on a discontinuous sucrose gradient revealed three membrane fractions, an outer membrane rich fraction, an inner membrane rich fraction and a fraction enriched with contact sites between the two membranes. The various glycosyltransferase systems involved in the biosynthesis of N-glycoproteins were located in these fractions.
    Biochemistry international 05/1989; 18(4):813-23.
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study yields evidence for the localization of a galactosyltransferase in purified liver plasma membranes, with the following results. The purified plasma membranes contained galactosyltransferases which transfered galactose from UDP-galactose into desialylated-degalactosylated fetuine. A suitable system of glycosylation reaction was defined. It contained: 10 mM Tris-HCl pH 7.4, 5 mM Mn2+, 4 mM NaF. For the assay with exogenous acceptors, 1.6 mg/ml of desialylated-degalactosylated fetuine and 0.1% of triton X-100 were added. The apparent Km values for UDP-galactose were about 10(-5) M. Enzymatic activities required Mn2+. This cation appeared to be a linear non-competitive activator when used at concentrations below 5 mM. Mg2+ and Ca2+ had an inhibitory effect on Mn2+-dependant-galactosyltransferase.
    Biochemistry international 03/1989; 18(2):415-28.
  • C Levrat, D Ardail, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: 1. In the mitochondria, the biosynthesis of N-glycoprotein products, through the dolichol intermediates pathway, appears in the outer and in the inner membranes. 2. The biosynthesis of dolichol-pyrophosphoryl-N-acetyl-glucosamine, dolichol-pyrophosphoryl-di-N-acetylchitobiose, dolichol-phosphoryl-glucose and dolichol-phosphoryl-mannose is effective in both membranes. 3. The lipid-linked oligosaccharides biosynthesized in both membranes contain high mannose-type oligosaccharides ranging in size from Man9-GlcNac2 to Man4-GlcNac2. 4. The assembly of the dolichol-pyrophosphoryl-oligosaccharides on the trimannosidic core begins by the elongation of the alpha-1,3 mannose branch in the outer membrane and of the alpha-1,6 mannose branch in the inner membrane.
    International Journal of Biochemistry 02/1989; 21(3):265-78.
  • [Show abstract] [Hide abstract]
    ABSTRACT: 1. Inner mitochondrial membranes are able to transfer [14C]glucose from UDP-[14C]glucose onto dolichylmonophosphate. 2. Synthesis of dolichyl-phosphoryl-glucose takes place only in the presence of exogenous dolichyl-monophosphate loaded into phospholipid vesicles. 3. Neutral phospholipids interact preferentially with the membrane-bound enzyme. The effect of phospholipids is not related to the length of fatty acid chains but a correlation between the activation and the degree of unsaturation of fatty acid chains has been found. 4. This enzyme required divalent cations for activity. Such a requirement might be related to lipid-protein interactions which favour a suitable conformation of glycosyltransferase.
    International Journal of Biochemistry 02/1989; 21(5):541-8.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The results reported in this paper show two distinct ways for the incorporation ofN-acetylglucosamine into mitochondrial outer membranes. The first one is the glycosylation of dolichol acceptors, which is indicated by the inhibition of the synthesis of these products by the inhibitors of the dolichol intermediates (tunicamycin and GDP). The second one is the incorporation ofN-acetylglucosamine into protein acceptors directly from UDP-N-acetylglucosamine. This second way of glycosylation is only localized in mitochondria outer membranes.The existence of a direct route forN-glycoprotein biosynthesis has been based on the following evidence. First, the synthesis of theN-acetylglucosaminylated protein acceptors was not inhibited by tunicamycin or GDP. Second, the addition of exogenous dolichol-phosphate did not change the rate of biosynthesis of glycosylated protein material. Third, the sequential incorporation ofN-acetylglucosamine and mannose from their nucleotide derivatives in the presence of GDP and tunicamycin led to the synthesis of glycosylated protein material which entirely bound to Concanavalin A-Sepharose. The oligosaccharide moiety of the glycosylated protein material resulting from the direct transfer of sugars from their nucleotide derivatives to the protein acceptor is of theN-glycan type. On sodium dodecylsulphate polyacrylamide gel electrophoresis, this glycosylated material migrated as a marker protein with a molecular weight between 45 000 and 63 000. HPLC chromatofocusing analysis revealed that the fraction studied was anionic. The oligosaccharide moiety of the glycoprotein material can only be elongated by the incorporation ofN-acetylglucosamine and galactose from their nucleotide derivatives.
    Glycoconjugate Journal 11/1988; 5(4):449-466. · 1.88 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: 1. Glucosyltransferase activity incorporating [14C]glucose from UDP-[14C]glucose onto endogenous lipidic acceptors was localized primarily in the plasma membrane of liver. 2. Incubation of plasma membrane by phosphatidyl-choline liposomes loaded with dolichyl-phosphate stimulated the enzymatic activity. 3. This enzyme required Mg2+ for maximal catalitic activity. Ca2+ could substitute Mg2+. 4. Mn2+ acted as a partial non-competitive inhibitor of the Mg2+-activated glucosyltransferase. 5. This enzyme can be modulated by neutral and acidic phospholipids; the most efficient were phosphatidyl-serine and phosphatidyl-inositol. 6. The enzymatic activity was not significantly changed by cholesterol alone but it is greatly enhanced by liposomes loaded with dolichyl-phosphate and cholesterol.
    International Journal of Biochemistry 02/1988; 20(9):951-8.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The enzyme GDPmannose: dolichyl monophosphate mannosyltransferase has been solubilized and purified from mice liver mitochondrial outer membranes. The purification combines detergent extraction of purified outer membranes using Nonidet P-40, with subsequent ion-exchange chromatography on DEAE-cellulose. At this stage, a 400-fold purification is obtained. The partially purified mannosyltransferase is activated by choline-containing lipids such as phosphatidylcholine, lysophosphatidylcholine and sphingomyelin. The reaction is dependent upon the addition of exogenous dolichyl monophosphate. The sole reaction product has been identified as dolichyl phosphate-mannose. The partially purified mannosyltransferase exhibits a Km of 1.33 microM for GDPmannose. Enzyme activity, eluted from DEAE-cellulose, could be further purified after incorporation into sphingomyelin vesicles containing dolichyl monophosphate followed by a sucrose density gradient centrifugation. The mannosyltransferase activity is completely associated with the liposomes at the top of the gradient. Significant stabilization and purification (approx. 1600-fold) of enzyme activity associated with these liposomes is obtained. Furthermore, the reconstitution of this purified enzyme within specific liposomes provides a good model membrane to investigate the molecular requirement of this mitochondrial mannosyltransferase.
    Biochimica et Biophysica Acta 10/1987; 925(3):297-304. · 4.66 Impact Factor
  • D Ardail, O Gateau, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: The role of phospholipids in the activity of inner mitochondrial mannosyltransferase was investigated. This enzyme catalyzes the direct transfer from GDP-mannose to lipidic acceptor. Inner mitochondrial membranes from purified mice liver mitochondria are prepared by digitonin treatment. Swelling of mitoplasts leads to the formation of inner membrane vesicles, which are then purified on a discontinuous sucrose gradient. The validity of this fractionation procedure is controlled by measurements of specific enzymatic activities and by electron microscopy. Measurement of mannosyltransferase activity in native inner mitochondrial membranes is unsuccessful, even in the presence of exogenous dolichyl monophosphate. Treatment of inner membranes with specific phospholipid liposomes in the presence of exogenous dolichyl monophosphate is essential in order to measure this enzymatic activity. Addition of phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and cardiolipin in the presence of Mg2+ results in a high degree of activation of the mannosyltransferase system. Maximal enzymatic activity is obtained with an approximate 3:7 mass ratio of exogenous phospholipid to inner membrane proteins. These experiments establish that sensitivity to activation by phospholipids is an inherent property of inner membrane mannosyltransferase. Another approach to this problem was to reconstitute an in vivo lipidic environment of the inner membrane. The results of this procedure suggest that the activity of inner mitochondrial mannosyltransferase may be subject to modulation by outer membrane lipidic extract treatment.
    European Journal of Biochemistry 07/1985; 149(3):497-502. · 3.58 Impact Factor
  • H Bador, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: Temperature dependence of asialomucin-sialyltransferase (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity is investigated. Discontinuities in Arrhenius plots are observed, whether the enzyme is membrane-associated or solubilized. These discontinuities cannot be firmly correlated with the phase-transition temperatures of either endogenous or exogenous phospholipids. Arrhenius plots of the kinetic parameters also exhibit sharp discontinuities, so that it is concluded that a significant change in Km and Vmax values occurs with varying temperature. Our results suggest that the biphasic behavior of Arrhenius plots may be attributed to the temperature dependence of the kinetic parameters for both membrane-associated and solubilized sialyltransferase activities.
    Biochimica et Biophysica Acta 08/1984; 800(1):75-86. · 4.66 Impact Factor
  • H Bador, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: The temperature dependence of sialyltransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetyl-neuraminyltrasferase, EC 2.4.99.1) inhibition is described when 1-palmitoyl-sn-glycero-3-phosphorylcholine, or a saturated fatty acid (lauric, myristic or palmitic acid) or an equimolar mixture of the two components are added. Lysophospholipid and fatty acids have no appreciable effect on the optimal temperature for sialyltransferase activity. In the presence of lysophospholipid, the membranous sialyltransferase activity is decreased for all the temperature range tested. In contrast, the solubilized sialyltransferase activity is decreased for temperatures exceeding 29 degrees C. In the presence of saturated fatty acids, the membranous activity is decreased above a chain-length dependent temperature: 22 degrees, 25 degrees and 30 degrees C for lauric, myristic and palmitic acids, respectively. In contrast, the solubilized activity remains unchanged. In the presence of equimolar mixtures of lysophospholipid and fatty acid, the membranous activity is decreased above the same critical temperature as that described for fatty acids added alone. In contrast, the solubilized activity is decreased above 29 degrees C. From these observations, it is suggested that lysophospholipid inhibits the solubilized enzyme when the temperature exceeds the critical micellar temperature of this lipid. The fatty acids inhibit the microsomal enzyme probably by incorporating into the membrane. It is also suggested that equimolar mixtures of lysophospholipid and fatty acid give rise to molecular analogs of 1,2-dipalmitoyl-sn-glycero-3-phosphorylcholine.
    Biochimie 04/1984; 66(3):223-33. · 3.14 Impact Factor
  • M Léon, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: We have shown that the fucosyltransferase activity was located in two subcellular fractions: the microsomes and the synaptosomes. The localization of enzyme activity was identical in the young and in the adult rat brain. The values of some parameters of the microsomal enzyme (Km, optimum temperature, optimum pH) in the young and in the adult rat brain shown that the enzyme affinity for its substrate is in relation with the brain maturation.
    Archives internationales de physiologie et de biochimie 08/1983; 91(2):121-5.
  • H Bador, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: Antineoplastic alkyl-lysophospholipids were found to exert a strong inhibitory effect on membranous or solubilized asialomucin-sialyltransferase (CMP-N-acetylneuraminate: D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity. This inhibitory effect was dependent on the presence of the choline moiety in position 3 of the glycerol molecule, as well as on the presence of long ether-linked aliphatic side chain in position 1 and the absence of any large substituent in position 2. As an example, 1-octadecyl-2-O-methyl-glycero-3-phosphorylcholine acted as a mixed-type inhibitor. Such an inhibitory process on sialyltransferase activity might be an additional factor in the tumor cell destructive effect of alkyl-lysophospholipids.
    International Journal of Biochemistry 02/1983; 15(9):1137-42.
  • M Léon, P Broquet, R Morélis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: GDP-fucose:asialofetuin fucosyltransferase activity was studied during the postnatal development of rat brain. The enzymatic activity was very low during the first days of life and reached a maximum level around 21 days. This increase in enzymatic activity was characterized by two periods of rapid change. A rapid increase occurred between 3 and 7 days after birth, followed by a slow increase from 7 to 17 days, then a new rapid change from 17 to 21 days. Stimulation of the enzymatic activity by Triton X-100 increased with age. The development profiles of GDP-fucose pyrophosphatase and fucosidase did not change during this period.
    Journal of Neurochemistry 01/1983; 39(6):1770-3. · 3.97 Impact Factor
  • H Bador, R Morelis, P Louisot
    [Show abstract] [Hide abstract]
    ABSTRACT: Asialomucin-sialyltransferase (CMP-N-acetylneuraminate:D-galactosyl-glycoprotein N-acetylneuraminyltransferase, EC 2.4.99.1) activity was solubilized from mouse liver microsomes by sonication. The catalytic activity was markedly inhibited by a series of lysophosphatidylcholines, particularly 1-palmitoyl-sn-glycero-3-phosphorylcholine. This lysophospholipid did not alter optimal conditions for enzyme activity. In contrast, it was found that affinities for binding of Mn2+, desialylated mucin and CMP-sialic acid were decreased by adding the lipid. A reasonable interpretation of these data is that the presence of phospholipid modifies the enzyme conformation.
    Biochimica et Biophysica Acta 09/1982; 706(1):36-41. · 4.66 Impact Factor

Publication Stats

99 Citations
85.21 Total Impact Points

Institutions

  • 1974–2008
    • University of Lyon
      Lyons, Rhône-Alpes, France
  • 1988–1990
    • Universidad de León
      • Department of Biochemistry and Molecular Biology
      León, Castile and Leon, Spain
  • 1985
    • French Institute of Health and Medical Research
      Lutetia Parisorum, Île-de-France, France