caa a22 4500 397520530 CHVBK 20180308164631.0 cr unu---uuuuu 161202e199511 xx s 000 0 eng 10.1093/jxb/46.11.1761 doi (NATIONALLICENCE)oxford-10.1093/jxb/46.11.1761 Binding of endoamylase to native starch grains from poplar wood [Elektronische Daten] [Wolfgang Witt, Anke Buchholz, Jörg J. Sauter] Starch grains were isolated from parenchyma cells of poplar wood (Populus × canadensis Moench ‘robusta'). The grains contained tightly bound amylase activity, which was classified as α-amylase (EC 3.2.1.1) by substrate specificity. The enzyme differs in some kinetic properties and the native electrophoresis profile from soluble amylase forms of the same material. The binding of α-amylase to isolated grains was affected by temperature and by maltose and malto-oligosaccharides in high concentrations. The amylase content of the grains was reduced to 18% as the temperature was increased from 1 °C to 31 °C, and 97% of the activity was released by a treatment with maltose at 20°C. The binding was fully reversible. The release of oligoglucans from starch grains was inhibited by removing the starch-associated amylase or by preventing the binding by addition of exogenous glucans, while the degradation of a soluble substrate — starch azure — was not affected by carbohydrates. These observations indicate that the granule-bound amylase is involved in the dissolution of starch and that binding to the grains is a prerequisite of the amylolytic activity. The results are consistent with the assumption that the amylase contains a raw starch binding site in addition to the active site. The exposure of excised twigs harvested in late autumn or winter to a low temperature regime led to an increase of the granule-bound amylase activity and to a simultaneous decrease of the starch level. It is therefore suggested that the reversible binding of the α-amylase to starch granules as affected by temperature and glucans might take part in the regulation of the starch content. © Oxford University Press RESEARCH PAPERS nationallicence Endoamylase nationallicence granular starch nationallicence poplar wood nationallicence starch-bound enzymes nationallicence starch degradation nationallicence Witt Wolfgang Botanisches Institut der Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany aut Buchholz Anke Botanisches Institut der Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany aut Sauter Jörg J. Botanisches Institut der Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany aut Journal of Experimental Botany Oxford University Press 46/11(1995-11), 1761-1769 0022-0957 46:11<1761 1995 46 exbotj https://doi.org/10.1093/jxb/46.11.1761 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1093/jxb/46.11.1761 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Witt Wolfgang Botanisches Institut der Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany aut NATIONALLICENCE 700 1- Buchholz Anke Botanisches Institut der Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany aut NATIONALLICENCE 700 1- Sauter Jörg J. Botanisches Institut der Universität Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany aut NATIONALLICENCE 773 0- Journal of Experimental Botany Oxford University Press 46/11(1995-11), 1761-1769 0022-0957 46:11<1761 1995 46 exbotj Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford