Fig. 2
From: Heat shock proteins and hormesis in the diagnosis and treatment of neurodegenerative diseases
Heme metabolism and HO-1 enzyme activity. HO-1 catalyze the rate-limiting step in heme metabolism. Heme is cleaved by HO-1 to yield equimolar quantities of iron, CO, and biliverdin. The regulatory actions of CO can be, at least in part mediated, by the activation of MAPK pathway. Biliverdin is converted to bilirubin by biliverdin reductase, this latter being also endowed with Ser/Thr/Tyr kinase activity through which regulates cell growth and metabolism. At low physiological concentrations, bilirubin behaves as a powerful antioxidant