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Carbon Monoxide — From Tool to Neurotransmitter
Published in David G. Penney, Carbon Monoxide, 2019
Nanduri R. Prabhakar, Robert S. Fitzgerald
More than four decades ago, Sjorstrand (1949) provided the first evidence for the endogenous formation of CO. It is formed as a by-product of the catalytic oxidation of the heme molecule. The enzyme heme oxygenase (HO), in concert with microsomal NADPH-cytochrome P-450 reductase and molecular oxygen, catalyzes the physiological degradation of heme (Figure 3). One of the three molecules of oxygen used during the enzymatic cleavage of heme is utilized to generate CO. Purified NADPH-cytochrome P-450 reductase alone can catalyze oxidative degradation of the heme molecule (Docherty et al., 1984; Kim et al., 1987; Yoshinaga et al., 1982). However, only a small amount of CO is produced via this route. Therefore, heme oxygenases are the major enzyme system responsible for endogenous CO formation.
Cellular Stress Responses Following Photodynamic Therapy
Published in Barbara W. Henderson, Thomas J. Dougherty, Photodynamic Therapy, 2020
Stefan W. Ryter, Charles J. Gomer, Angela Ferrario, Anita M. R. Fisher, Marian Luna, Natalie Rucker, Sam Wong
Heme oxygenase, a microsomal enzyme, catalyzes the oxidative degradation of heme to biliverdin, liberating the α-methene bridge carbon as carbon monoxide [25]. NADPH: biliverdin reductase completes heme catabolism by reducing biliverdin to bilirubin, which upon glucuronidation, passes from the body by the biliary-fecal route [20]. An antioxidant role has been suggested for heme oxygenase on the basis that bilirubin and biliverdin have plasma antioxidant (peroxyl radical scavenging) properties, though this probably has little in vitro significance [26].
Physiological and pathophysiological implications of hydrogen sulfide: a persuasion to change the fate of the dangerous molecule
Published in Journal of the Chinese Advanced Materials Society, 2018
Jan Mohammad Mir, Ram Charitra Maurya
Carbon monoxide, on the other hand, was also considered as harmful, causing asphyxiation and was been labeled as silent killer. It is a by-product formed by burning of fossil fuels and tobacco.[11] The high affinity of CO to hemoglobin (Hb) is 240 times greater that of oxygen forming carboxyhemoglobin (COHb).[12, 13] This results in tissue hypoxia and death.[14, 15] In 1968 proposed endogenous production of CO from heme catalysis opened fascination toward the molecule.[16] The endogenous synthesis of CO was accepted as a metabolic waste product of heme degradation catalyzed by heme oxygenase (HO).[17] The remarkable breakthrough discovered in 1987, when Brune and Ullrich[18] showed that, like NO, CO can also activate soluble guanylate cyclase (sGC) laid the foundation for the next discovery in 1993 when Verma et al.[19] showed that CO, again like NO, might also have a physiological role to play. Some of the main roles have been given in Figure 2. Since then, anti-inflammatory, anti-apoptotic, and anti-proliferative properties of CO have emerged out.[11]