Cytochrome oxygen activation

Owing to the fact that ethyl ethers are especially effective substrates for CYP1A1 [184], the probe possesses an ethyl group on the phenolic oxygen of the trimethyl lock. In vitro, fluorescence was manifested by CYP1A1 isozyme with Kcat/KM 8.8 x 103 M-1s 1 and KM 0.09 pM. In cellulo, the probe revealed the induction of cytochrome P450 activity by the carcinogen 2,3,7,8-tetrachlorodi-benzo-p-dioxin (TCDD), and its repression by the chemoprotectant resveratrol. 

The parasitic nematode, Ascaris suum, undergoes a number of well-characterized metabolic transitions during its development (Table 14.1), but little is known about the regulation of these events (Barrett, 1976 Komuniecki and Komuniecki, 1995). Adults reside in the porcine small intestine and fertilization takes place under low oxygen tensions. The unembryonated egg that leaves the host is metabolically quiescent, has no detectable cytochrome oxidase activity or ubiquinone and appears to be transcriptionally inactive (Cleavinger et al., 1989 Takamiya et al., 1993). Embryonation requires oxygen and after about 48-72 h is accompanied by... 

Orrenius, S. and Ernster, L. Microsomal cytochrome P-l+50-linked monooxygenase systems in mammalian tissues. In Hayaishi, 0. (Ed.) Molecular Mechanisms of Oxygen Activation (197 0 Academic Press, New York, pp 215-21+1+. 

Proposed model for oxygen activation in cytochrome P450. Reduction by a single electron enables the ferrous iron to bind oxygen. Addition of a second electron generates an iron peroxide heme, which then cleaves to form water and an electrophilic perferryl species. 

Makris TM, Davydov R, Denisov IG, et al. Mechanistic enzymology of oxygen activation by the cytochromes p450. Drug Metab Rev 2002 34 691-708. 

Babcock, G.T. Wickstrom, M. (1992) Oxygen activation and the conservation of energy in cell respiration. Nature 356, 301-309. Advanced discussion of the reduction of water and pumping of protons by cytochrome oxidase. 

Poulos, T. L. Raag, R. (1992). Cytochrome P450cam crystallography, oxygen activation, and electron transfer. Federation of American Society Experimental BiologyJournal, 6,674-9. 

Active fish have a better developed capillary system in the red muscle to supply oxygen to the mitochondria, and a higher haematocrit (Blaxter et al., 1971). The red muscle tissue also contains more cytochromes (respiratory proteins), and exhibits more cytochrome oxidase activity, which is responsible for transferring electrons in die respiratory chain, more efficient respiration control (oxidative phosphorylation and P/O coefficient) and a greater Atkinson charge, which characterizes energy reserve accumulated in adenyl nucleotides ... 

Studies of the Mechanism of Oxygen Activation and Transfer Catalyzed by Cytochrome P 450... 

The focus of this chapter is the reaction site of oxygenases (hemo-proteins) having heme as the prosthetic group. We discuss the oxygen activation in tryptophan pyrrolase (TPO) and cytochrome P-450 based on our experimental results using iron-porphyrin complexes as the model for the active site of these enzymes. 

Yeom, H. Y., and Sligar, S. G. 1997 Oxygen activation by cytochrome P450(BM-3) Effects of mutating an active site acidic residue. Arch. Biochem. Biophys., 337, 209-216. 

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