Cytochrome microbial

Many examples of microbial hydroxylation of sterols/steroids have been reported. These hydroxylations usually involve mixed function oxidases which utilise molecular oxygen and cytochrome P-450. The reaction can be represented by ... 

FIGURE 3.1 Bacterial oxygenation systems (excluding cytochrome P450 systems). (From Neilson, A.H. and Allard, A.-S. Microbial metabolism of PAHs and heteroarenes, The Handbook of Environmental Chemistry, Vol. 3J, pp. 1-80, Springer, 1998. With permission.)... 

Sariaslani FS (1991) Microbial cytochromes P-450 and xenobiotic metabolism. Adv Appl Microbiol 36 133-177. 

Hubl, U. and Stevenson, D.E. (2001) In vitro enzymic synthesis of mammalian liver xenobiotic metabolites catalyzed by ovine liver microsomal cytochrome P450. Enzyme and Microbial Technology, 29, 306-311. 

Torres, E. Sandoval, J. V. Rosell, F. I., et al., Site-Directed Mutagenesis Improves the Biocatalytic Activity of Iso-l-Cytochrome-C in Polycyclic-Hydrocarbon Oxidation. Enzyme and Microbial Technology, 1995. 17(11) pp. 1014—1020. 

Tinoco, R., and VazquezDuhalt, R., Chemical Modification of Cytochrome C Improves Their Catalytic Properties in Oxidation of Polycyclic Aromatic Hydrocarbons. Enzyme and Microbial Technology, 1998. 22(1) pp. 8-12. 

Vazquez-Duhalt, R. Semple, K. M. Westlake, D. W. S., and Fedorak, P. M., Effect of Water-Miscible Organic-Solvents on the Catalytic Activity of Cytochrome-C. Enzyme and Microbial Technology, 1993. 15(11) pp. 936-943. 

Recent work in our laboratories has confirmed the existence of a similar pathway in the oxidation of vindoline in mammals (777). The availability of compounds such as 59 as analytical standards, along with published mass spectral and NMR spectral properties of this compound, served to facilitate identification of metabolites formed in mammalian liver microsome incubations. Two compounds are produced during incubations with mouse liver microsome preparations 17-deacetylvindoline, and the dihydrovindoline ether dimer 59. Both compounds were isolated and completely characterized by spectral comparison to authentic standards. This work emphasizes the prospective value of microbial and enzymatic transformation studies in predicting pathways of metabolism in mammalian systems. This work would also suggest the involvement of cytochrome P-450 enzyme system(s) in the oxidation process. Whether the first steps involve direct introduction of molecular oxygen at position 3 of vindoline or an initial abstraction of electrons, as in Scheme 15, remains unknown. The establishment of a metabolic pathway in mammals, identical to those found in Strep-tomycetes, with copper oxidases and peroxidases again confirms the prospective value of the microbial models of mammalian metabolism concept. 

Smital T, Luckenbach T, Sauerborn R, Hamdoun AM, Vega RL, Epel D (2004) Emerging contaminants - pesticides, PPCPs, microbial degradation products and natural substances as inhibitors of multixenobiotic defense in aquatic organisms. Mutat Res 552 101-117 Snyder MJ (2000) Cytochrome P450 enzymes in aquatic invertebrates recent advances and future directions. Aquat Toxicol 48 529-547... 

Although mammalian CYPs are attractive candidates for use as commercial biocatalysts, many functional characteristics limit the opportunities to exploit such a system. Association of the enzymes with membranes prevents easy extraction and purification and limits the opportunities to produce useful recombinant enzymes by cloning the relevant genes for expression in microbial systems. All P450s have a porphyrin-haem active site that requires a second protein to reduce the iron component, often cytochrome P450 reductase or... 

Two different enzyme systems have been described, one uses cytochrome P-450 to activate oxygen whereas the other employs flavin adenine dinucleotide (FAD). Both the cytochrome P-450 and the flavin monooxygenase systems have broad substrate specificities and oxidize and oxygenate a variety of organic nitrogen or sulfur compounds. The enzymes have a widespread distribution and have been detected in animals, plants, fungi and bacteria. Their function appears to be primarily one of detoxification of xenobiotics. Microbial enzymes... 

Several crystal structures of microbial cytochrome P450 enzymes are now available [45, 48-50], The first X-ray structure for P450 was that of cytochrome P450cam... 

Biofuel cells — Figure. Schematic illustration of identified electron transfer mechanisms in microbial fuel cells. Electron transfer via (a) cell membrane-bound cytochromes, (b) electrically conductive pili (nanowires), (c) microbial redox mediators, and (d) via oxidation of reduced secondary metabolites [v]... 

---