Nitrosative modifications modulate the activity of plant aminoaldehyde dehydrogenase

Reactive nitrogen species (RNS) are signalling molecules triggering several defence responses during plant stress. The highest importance has nitric oxide (NO), involved in the post-translational modifications, including protein S-nitrosation of target cysteine residues. Aminoaldehyde dehydrogenases (AMADHs) catalyze the NAD(P)⁺-dependent oxidation of various ω-amino aldehydes to the corresponding amino acids. Here, we focused on the dynamic redox regulation of AMADH activity in pea (Pisum sativum). We used the reversible S-nitrosation approach and studied the effect of NO donors on the activity of two AMADHs. LC-MS/MS analysis combined with structural mapping revealed selective modification of spatially accessible cysteine residues, whereas the catalytic Cys294 was detected predominantly in the methylthionylated form, consistent with its largely reduced state under the applied experimental conditions. These findings suggest that S-nitrosation modulates PsAMADH activity in a structurally constrained manner without directly disrupting the catalytic core. Inhibition of AMADH activity in roots of different pea genotypes was accompanied by increased RNS/NO accumulation, suggesting that nitrosative modulation of PsAMADH activity represents an important component of redox regulation in vivo.