Characterization of Isoforms of Pectin Methylesterase of Linum usitatissimum Using Polyclonal Antibodies

In flax (Linum usitatissimum, c.v. Ariane) pectin methylesterase(PME) (EC 3.1.1.11 EC] ), ionically bound to cell-wall, was composedmainly of forms with isoelectric points (pIs) of 7.1, 7.6 and9.6. Minor forms, with acid pIs (4.5, 4.8 and 6.3), were detectedduring the purification of two of these forms. Polyclonal antibodieswere raised against the isoenzymes presenting pIs of 7.1 and7.6. Antibodies recognized antigenic forms and two close proteinsin the basic range which could be associated to the PME activitywith pI of 9.6. Antibodies did not recognize any acid formsand exhibited no cross-reactivity with proteins resolved inthe cellular content. Antigenicity was related mainly to theprotein part of the glycosylated enzyme. The antibodies againstflax PME did not cross-react with PMEs from Citrus and tomatoand with glycosylated proteins of various sources. Specificityof anti-PME antibodies was judged sufficient to localize therecognized forms on tissue prints of flax hypocotyls. AlthoughPME was distributed in the whole parts of hypocotyl, stainingwas not homogeneous and appeared reinforced in the apical zone.In the basal part, epidermis was more contrasted than internaltissues. (Received August 2, 1994; Accepted January 3, 1995)