Nitrotyrosine

3-nitrotyrosine (3-NT) is a stable end-product of tyrosine modification by peroxynitrite (formed from nitric oxide and superoxide), serving as a footprint of reactive nitrogen species (RNS) attack on proteins and a validated biomarker of nitrosative stress and protein nitration. In exercise physiology, salivary 3-nitrotyrosine rises in proportion to exercise intensity and duration, reflecting the combined generation of NO from muscle nNOS activation and superoxide from mitochondrial and xanthine oxidase sources during high-intensity training. Valavanidis et al. (2009) established protein nitration markers including nitrotyrosine as critical components of the oxidative stress biomarker panel.