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Media type:
E-Article
Title:
Glucan-phosphorylase forms in cotyledons of Pisum sativum L.: Localization, developmental change, in-vitro translation, and processing
Contributor:
van Berkel, Joachim;
Conrads-Strauch, Jutta;
Steup, Martin
imprint:
Springer-Verlag, 1991
Published in:Planta
Language:
English
ISSN:
0032-0935;
1432-2048
Origination:
Footnote:
Description:
<p>The occurrence, location, and biosynthesis of glucan-phosphorylase (EC 2.4.1.1) isoenzymes were studied in cotyledons of developing or germinating seeds of Pisum sativum L. Type-I and type-II isoenzymes were detected, and were also localized by indirect immunofluorescence using polyclonal anti-type-I or anti-type-II phosphorylase antibodies. Type-I isoenzyme was found in the cytosol of parenchyma cells whereas the type-II enzyme form is a plastid protein which resides either in amyloplasts (in developing seeds) or in proplastids (in germinating seeds). During seed development, type-II phosphorylase was the predominant isoenzyme and the type-I isoenzyme represented a very minor compound. During germination, the latter increased whilst type-II phosphorylase remained at a constant level. In in-vitro translation experiments, type-I isoenzyme was observed as a final-size product with an apparent molecular weight of approx. 90 kDa. In contrast, type-II phosphorylase was translated as a high-molecular-weight precursor (116 kDa) which, when incubated with a stromal fraction of isolated intact pea chloroplasts, was processed to the size of the mature protein (105 kDa).</p>