**3. Phosphorylation of mitochondrial proteins as a regulatory mechanism of energy metabolism during ischemia/reperfusion**

Numerous mitochondrial proteins (354 reported to date) are phosphoproteins that collectively contain 899 identified and 479 potential novel phosphorylation sites [18, 19]. Consequently, phosphorylation of mitochondrial proteins has emerged as an important mechanism involved in progressive damage of mitochondria in response to metabolic stresses including I/R and the status of these phosphorylations is key to understanding the regulation of mitochondrial functions in disease states [18, 19]. A number of protein kinases localize to mitochondria in response to I/R [19, 20]. Protein phosphorylations by these kinases produce differential outcomes in different tissues depending on the phosphorylation site and the kinase involved. The key proteins of oxidative phosphorylation, TCA cycle, transport, and the cascade of intrinsic apoptosis are regulated by phosphorylation [19–23].
