Rubisco Activation is Impaired in Transgenic Tobacco Plants with Reduced Electron Transport Capacity

Rubisco can be catalytically competent only after a specific lysyl residue within the active site has been carbamylated. Before carbamylation can occur, any inhibitory ligands bound at the site must be released, and this process is facilitated by another enzyme, Rubisco activase. It has been shown in vitro that Rubisco activase needs to hydrolyse ATP to function and is inhibited by ADP, and so presumably is sensitive to the chloroplast ATP/ADP ratio (1). However, there are indications that activase is also regulated by transthylakoid pH gradient (∆pH) and electron transport through PSI (2).