Mammalian metabolism, microbial models

Several approaches are utilized in the development of microbial models of mammalian metabolism. The model could be either retrospective, prospective, or parallel in relation to the mammalian studies [26]. 

Smith RV. Rosazza J.P. (1975) Microbial models of mammalian metabolism. Pharm Sci, 64, 1737-1759. 

Rosazza JP, Rammer M, Youel L (1977) Microbial models of mammalian metabolism 0-demethylations of papaverine. Xenobiotica 7(3) 133-143... 

Moussa C et al. (1997) Microbial models of mammalian metabolism. Fungal metabolism of phenolic and nonphenolic p-cymene-related drugs and prodrugs. 11. Metabolites of nonphenolic derivatives. Drug Metab Dispos 25(3) 311-316... 

In the 1970s, Smith and Rosazza introduced the concept of microbial models of mammalian metabolism [38,39]. Two reviews in this area were published in 1999 [40,41]. Since these, there have been numerous reports describing the use of microbial biotransformation in drug metabolism studies [42-54]. These reports demonstrated that microbial enzymes were able to... 

Abourashed, E.A., Clark, A.M. and Hufford, C.D. (1999) Microbial models of mammalian metabolism of xenobiotics an updated review. Current Medicinal Chemistry, 6, 359-374. 

Rao, G.P. and Davis, P.J. (1997) Microbial models of mammalian metabolism biotransformation of HP 749 (besipirdine) using Cunninghamella elegans. Drug Metabolism and Disposition The Biological Fate of Chemicals, 25, 709-715. 

The concept of microbial models of mammalian metabolism was elaborated by Smith and Rosazza for just such a purpose (27-32). In principle, this concept recognizes the fact that microorganisms catalyze the same types of metabolic reactions as do mammals (32), and they accomplish these by using essentially the same type of enzymes (29). Useful biotransformation reactions common to microbial and mammalian systems include all of the known Phase I and Phase II metabolic reactions implied, including aromatic hydroxylation (accompanied by the NIH shift), N- and O-dealkylations, and glucuronide and sulfate conjugations of phenol to name but a few (27-34). All of these reactions have value in studies with the alkaloids. 

Strategy in Using Microbial Models of Mammalian Metabolism. In... 

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. 

Hezari, M., Davies, P.J. Microbial models of mammalian metabolism. Furosemide glucoside formation using the fungus Cunninghamella elegans. Drug Metab. Disp. 1993, 21 259-267. 

Many of the enzyme/microorganism mediated dealkylation procedures that have been reported have come from the work of Rosazza and his coworkers as a consequence of their studies on Microbial models on Mammalian metabolism. These studies have largely concerned with demethylation of various alkaloids with bacteria and fungi. 0-deethylation reactions with Streptomyces griseus as with dealkylation of 7-ethoxy coumarin gave very poor yields and therefore was not considered a viable synthetic procedure. The quinone imine(I), has been prepared in 64%isolated yield by horseradish peroxidase/hydrogen peroxide O-demethylation of 9-methoxy-ellipticine(II). Studies with H2 0 as a reaction medium demonstrated that the reaction was not a simple demethylation but rather a replacement of the methoxy group by OH from the solvent (as shown in Fig.l)... 

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