Tyrosine nitration provokes inhibition of sunflower carbonic anhydrase (β-CA) activity under high temperature stress.

Protein tyrosine nitration is a post-translational modification (PTM) mediated by reactive nitrogen species (RNS) and it is a new area of research in higher plants. Previously, it was demonstrated that the exposition of sunflower (Helianthus annuus L.) seedlings to high temperature (HT) caused both oxidative and nitrosative stress. The nitroproteome analysis under this stress condition showed the induction of 13 tyrosine-nitrated proteins being the carbonic anhydrase (CA) one of these proteins. The analysis of CA activity under high temperature showed that this stress inhibited the CA activity by a 43%. To evaluate the effect of nitration on the CA activity in sunflower it was used 3-morpholinosydnonimine (SIN-1) (peroxynitrite donor) as the nitrating agent. Thus the CA activity was inhibited by 41%. In silico analysis of the pea CA protein sequence suggests that Tyr(205) is the most likely potential target for nitration.