Influence of the activation status and of ATP on phosphoribulokinase degradation

Kamber, Lea; Feller, Urs (1998). Influence of the activation status and of ATP on phosphoribulokinase degradation. Journal of Experimental Botany, 49(319), pp. 139-144. Oxford University Press 10.1093/jxb/49.319.139

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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.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Plant nutrition (discontinued)
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)

UniBE Contributor:

Feller, Urs

Subjects:

500 Science > 580 Plants (Botany)

ISSN:

0022-0957

Publisher:

Oxford University Press

Language:

English

Submitter:

Peter Alfred von Ballmoos-Haas

Date Deposited:

06 Jul 2017 14:06

Last Modified:

23 Oct 2018 08:41

Publisher DOI:

10.1093/jxb/49.319.139

Uncontrolled Keywords:

ATP, enzyme inactivation, phosphoribulokinase, proteolysis, redox modulation

BORIS DOI:

10.7892/boris.91867

URI:

https://boris.unibe.ch/id/eprint/91867

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