Carbon monoxide, binding

FIGURE 15.26 Oxygen and carbon monoxide binding to the heme group of myoglobin. 

Table 21 Carbon monoxide binding constants3 and carbonyl vibrational frequencies in CH3CN at 25 °C.

The structural and functional integrity of organoclay-wrapped Mb and Hb molecules was demonstrated by retention of the secondary protein structure as well as distinctive shifts in the absorption spectra associated with oxygen or carbon monoxide binding to the heme metallocenter. The latter indicated that the wrapped... 

Omura, T. and Sato, R. (1964) The carbon monoxide-binding pigment of liver microsomes. I. Evidence for its hemoprotein nature. Journal of Biological Chemistry, 239, 2370-2378. 

Omura, T. and Sato, R. The carbon monoxide-binding pigment... 

Bennett B, Lemon BJ, Peters JW. 2000. Reversible carbon monoxide binding and inhibition at the active site of the Fe-only hydrogenase. Biochemistry 39 7455-60. 

Carbon monoxide binds to cytochrome a/Oj but less tightly than cyanide. It also binds to hemoglobin, displacing oxygen. Symptoms include headache, nausea, tachycardia, and tachypnea. Lips and cheeks turn a cherry-red color. Respiratory depression and coma result in death if not treated by giving oxygen. Sources of carbon monoxide include ... 

The electron transport chain is vital to aerobic organisms. Interference with its action may be life threatening. Thus, cyanide and carbon monoxide bind to haem groups and inhibit the action of the enzyme cytochrome c oxidase, a protein complex that is effectively responsible for the terminal part of the electron transport sequence and the reduction of oxygen to water. 

Carbon monoxide Binds to hemoglobin, reducing oxygen delivery to tissues Headache, dizziness, nausea, vomiting, seizures, coma... 

Carbonyl Vibrational Frequencies and Carbon Monoxide Binding Constants for Nickel(I) Carbonyl Complexes of Macrocycuc Ligands... 

In the reduced state, cytochromes P-450 may also bind certain ligands to give particular difference spectra. The most well known is that which occurs when carbon monoxide binds giving an absorption maximum at 450 nm. A type III spectrum gives two peaks at 430 and 455 nm after binding of certain compounds such as ethyl isocyanide or methylenedioxyphenyl compounds to the reduced enzyme. The latter form stable complexes with the enzyme and are also inhibitors. 

In vitro. The activity or absolute level of enzymes such as cytochrome P-450 and glucuronosyl transferase can be measured in cells, tissue fractions, or subcellular fractions (e.g., microsomes) and compared with those from control animals. The activity is measured by using a particular substrate for each of the isoforms of the enzyme (e.g., cytochrome P-450 or UDPGT) of interest. The total level of cytochrome P-450 could be determined by spectrophotometry using standard methods (e.g., carbon monoxide binding and difference spectra). Alternatively, the level of protein can be determined by gel electrophoresis and Western blotting, and this would allow the separation of different isoforms. 

The mechanism underlying carbon monoxide poisoning is well understood at the biochemical level. Carbon monoxide binds to the iron atom in hemoglobin at the same binding site as oxygen, but it binds more avidly, indeed about 240 times more strongly. The product is carboxyhemoglobin, which may contain one or more carbon monoxide molecules. 

Figure 7.66 The heme moiety of the hemoglobin molecule showing the binding of the oxygen molecule to the iron atom. As shown in the diagram, carbon monoxide binds at the same site. Abbreviation His, side chain of the amino acid histidine. Source From Ref. 18.

Fig. 9. Arrhenius plots of the logarithmic, , rate of carbon monoxide binding to microperoxidase and of log T/T) (tj = viscosity) against inverse temperature, T 1,...

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