Oxidative/nitrative stress-mediated modifications in a protein play important roles in a wide range of cellular, physiological, and pathological processes (Dalle-Donne et al., 2005; Dalle-Donne, Scaloni, & Butterfield, 2006). Protein tyrosine nitration is an important redox-related modification that alters activity of a protein. Endogenous nitrotyrosine-containing proteins and nitrotyrosine-sites have been identified in differential pathophysiological conditions, including several main categories (Table 1). (1) Tyrosine nitration is clearly involved in tumorigenesis. Nine nitroproteins, three nitroprotein-interacted proteins, and ten nitrotyrosine sites were identified from a pituitary adenoma (Zhan & Desiderio, 2006), and eight nitroproteins were identified from human pituitary control tissue (Zhan & Desiderio, 2004, 2007) (Table 2). Nitrated protein was also identified in human gliomas (Fiorce et al., 2006) and rat glioma cell lines (Nakagawa et al., 2007). (2) Tyrosine nitration is involved in aging and aging-related diseases. Nitrotyrosine-containing proteins were discovered in aging rat skeletal muscle (Kanski, Hong, & Schoneich, 2005; Sharov et al., 2006), rat heart (Kanski et al., 2005), and mouse liver (Marshall et al., 2013). (3) Tyrosine nitration is involved in inflammation-related diseases. Nitrotyrosine-containing proteins were identified in a septic patient's rectus abdominis muscle (Lanone et al., 2002), bronchial epithelial cells and bronchoalveolar lavage with asthma (Ghosh et al., 2006), Chagas' disease (Dhiman et al., 2008), experimental sepsis (Chatterjee et al., 2009), and serum sample of a C57BL6/J mouse model with septic shock (Ghesquiere et al., 2009). (4) Tyrosine nitration is involved in neurodegenerative diseases. Nitrotyrosine-containing proteins were identified in mouse brain (Sacksteder et al., 2006; Bigelow & Qian, 2008; Zhang et al., 2010), spinal cords of a mouse model of familial amyotrophic lateral sclerosis (Casoni et al., 2005), Parkinson's disease (Danielson et al., 2009), and HT22 hippocampal cells (Yoon et al., 2010). (5) Tyrosine nitration is involved in the neurovisual system. Nitroproteins were identified in SOD2-knockdown mouse eye-cup (Justilien et al., 2007), photoreceptor rod outer segments (Palamalai et al., 2006), and human Bruch's membrane (Murdaugh et al., 2010). (6) Tyrosine nitration is also involved in the cardiovascular system and related diseases. For example, nitroproteins have been indentified in ischemia reperfusion injury (Liu et al., 2009; Chen et al., 2008; Tao et al., 2013), vascular (Ai et al., 2008), and mouse heart (Bigelow & Qian, 2008; Zhang et al., 2010). (7) Tyrosine nitration is involved in kidney disease. Nitroproteins have been identified in a kidney disease patient's plasma (Piroddi et al., 2011). (8) Tyrosine nitration is involved in diabetes. Nitroproteins have been discovered in diabetic rats (Lu et al., 2010), diabetic mellitus patients (Safinowski et al., 2009), and a diabetic patient's urine (Kato et al., 2009). (9) Plants. Nitroproteins were discovered in plant disease (Cecconi et al., 2009; Chaki et al., 2009). (10) Others. Nitroproteins were discovered in sickle cell disease (Aslan et al., 2003), traumatic brain-injured rats (Reed et al., 2009), rat hippocampus after acute inhalation of combustion smoke (Lee et al., 2009a), Eosinophil granule toxins (Ulrich et al., 2008), hypertriglyceridemia (Casanovas et al., 2009), placenta/pre-eclampsia (Webster, Brockman, & Myatt, 2006), human plasma (Hamilton et al., 2008; Hui et al., 2012), murine liver (Zhu et al., 2008), rabbit muscle (Sharov et al., 2009), human hemoglobin associated with cigarette (Chen & Chen, 2012), human peripheral blood mononuclear cells (Ohama & Brautigan, 2010), mast cells (Sekar et al., 2010), and endothelial cells (Redondo-Horcajo et al., 2010).