Abstract
The role of glutathionylation of fructose-1, 6-bisphosphate aldolase (FBA) in chloroplasts was investigated. The Arabidopsis genome includes three genes for chloroplastic FBAs, of which glutathionylated FBA was designated as FBA1. Recombinant FBA1 activity had a strongly pH-dependency, which suited stromal pH that changes from 7 to 8 following illumination: FBA1 activity at pH 8 was 2-fold higher than at pH 7. Glutathione (GSH) strengthened this pH-dependency by 250 %. Other FBAs did not have such features. Thioredoxin (Trx) activates the Calvin cycle, but dithiothreitol and Trx inhibited the activity of three FBAs. At pH 8, GSH reactivated FBA1 only via glutathinonylation. FBA activity in wild-type chloroplasts was regulated by GSH and pH as was FBA1, while that in a T-DNA inserted mutant of FBA1 was little affected by GSH or pH. Altogether, FBA1 is expressed in vivo and regulated via glutathionylation to activate and facilitate the Calvin cycle.
