Xyloglucan endotransglucosylase/hydrolases (XTHs) are inactivated by binding to glass and cellulosic surfaces, and released in active form by a heat-stable polymer from cauliflower florets
Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved.
| Veröffentlicht in: | Journal of plant physiology. - 1979. - 218(2017) vom: 15. Nov., Seite 135-143 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2017
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| Zugriff auf das übergeordnete Werk: | Journal of plant physiology |
| Schlagworte: | Journal Article Arabinogalactan-proteins Cell expansion Cell wall modification Cellulose binding Xyloglucan Xyloglucan endotransglucosylase/hydrolase Plant Proteins Polymers Cellulose mehr... |
| Zusammenfassung: | Copyright © 2017 The Authors. Published by Elsevier GmbH.. All rights reserved. Xyloglucan endotransglucosylase (XET) activity, which cuts and re-joins hemicellulose chains in the plant cell wall, contributing to wall assembly and growth regulation, is the major activity of XTH proteins. During purification, XTHs often lose XET activity which, however, is restored by treatment with certain cold-water-extractable, heat-stable polymers (CHPs), e.g. from cauliflower florets. It was not known whether the XTH-activating factor (XAF) present in CHPs works by promoting (e.g. allosterically) XET activity or by re-solubilising sequestered XTH proteins. We now show that XTHs in dilute solution bind to diverse surfaces (e.g. glass and cellulose), and that CHPs can re-solubilise the bound enzyme, re-activating it. Cell walls prepared from cauliflower florets, mung bean shoots and Arabidopsis cell-suspension cultures each contained endogenous, tightly bound, inactive XTHs, which were likewise rapidly solubilised (within 0.5h) and thus activated by cauliflower XAF. We present a convenient quantitative assay for XAF acting on the native sequestered XTHs of Arabidopsis cell walls; using this assay, we show that CHPs from all plants tested possess XAF activity. The XAF activity of diverse CHPs does not correlate with their conductivity, showing that this activity is not a simple ionic effect. The XAF action of cauliflower CHPs was augmented by NaCl, although NaCl alone was much less effective than a CHP solution of similar conductivity, confirming that the cauliflower polymers did not simply exert a salt effect. We suggest that XAF is an endogenous regulator of XET action, modulating cell-wall loosening and/or assembly in vivo |
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| Beschreibung: | Date Completed 14.05.2018 Date Revised 29.01.2022 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1618-1328 |
| DOI: | 10.1016/j.jplph.2017.07.022 |