Evidence for Several Galactan Synthases in Flax (Linum usitassimum L.) Suspension-Cultured Cells |
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Authors: | Goubet, Florence Morvan, Claudine |
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Affiliation: | Equipe "Parois et Polymres Paritaux", SCUEOR URA 203 CNRS, Facult des Sciences, Universit de Rouen 76821 Mont Saint-Aignan Cdex, France |
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Abstract: | A membrane fraction from flax cells was able to incorporate[14C]galactose from UDP-D-[14C]galactose in vitro. The productsof the reaction, characterized by methylation analysis, consistedof a rß-1,4-galactan (solubilized mainly in water)and a rß-1,3- rß-1,6-galactan (solubilizedmainly in alkali). These results indicated the presence of severalgalactan synthase complexes, as did a profile of the relationshipbetween pH and activity which revealed both a maximum at pH6.5 and a shoulder at pH 8. Moreover, galactan synthase activitieswere found at two densities: 1.125 g cm3 (Golgi membranes)and 1.071.08 g cm3 (corresponding to low-densityvesicles). Partial characterization of one enzymatic system (maximaly activeat pH 8 in the presence of 5 mM MgCl2) was achieved. The Kmfor UDP-galactose and Vmax were 38 µM and 4.5 nmol h1(mg protein)1, respectively. (Received June 6, 1993; Accepted September 22, 1993) |
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