naa a22 4500 53003526X 20181024074429.0 cr unu---uuuuu 181024e19980201xx s 000 0 eng 0022-0957 10.1093/jxb/49.319.139 doi (BORIS)oai:boris.unibe.ch:91867 580 ddc Kamber Lea Influence of the activation status and of ATP on phosphoribulokinase degradation [Elektronische Daten] [Lea Kamber, Urs Feller] publishedVersion openAccess eu-repo The light-regulated choroplast enzyme phosphoribulokinase (EC 2.7.1. 19) exists in two forms. In darkness this enzyme is present in an oxidized form, which is inactive. It is activated in the light by a thioredoxin-mediated reduction. In extracts from young wheat leaves (Triticum aestivum L.) phosphoribulokinase as well as some other thioredoxin-modulated enzymes can be activated by the artificial reductant dithiothreitol (DTT). The influence of the activation status and of the substrate ATP on phosphoribulokinase stability was investigated in the presence of endogenous endopeptidases from senescing wheat leaves. Similar experiments were performed with purified phosphoribulokinase from spinach in the presence of exogenous, purified endopeptidases (chymotrypsin and trypsin). Phosphoribulokinase stability was analysed by immunoblotting and activity measurements. Both systems led to similar conclusions. DTT (reductant) and ATP (substrate) stabilized phosphoribulokinase in wheat leaf extracts as well as partially purified phosphoribulokinase from spinach. The combination of both effecters was far more protective than either effector alone. DTT had hardly any effect on the degradation of thioredoxin-independent chloroplast enzymes such as glutamate synthase and glutamine synthetase. These results suggest that the activation status and substrate concentrations are not only important for the activity of phosphoribulokinase, but are also relevant for the susceptibility of this enzyme to proteolysis. Feller Urs joint author Journal of Experimental Botany 49(319), pp. 139-144 0022-0957 https://boris.unibe.ch/91867/1/JExpBot_49_319.pdf text/html WWW-Backlink auf das Repository 1 info:eu-repo/semantics/article boris PeerReviewed boris peerstatus BORIS 856 40 https://boris.unibe.ch/91867/1/JExpBot_49_319.pdf text/html WWW-Backlink auf das Repository BORIS 100 1- Kamber Lea BORIS 700 1- Feller Urs joint author BORIS 773 0- Journal of Experimental Botany 49(319), pp. 139-144 0022-0957 SWISSBIB 398419590 BK010053 XK010053 XK010000 BORIS BORIS BORIS info:eu-repo/semantics/article openAccess