Enzymology of N-Oxide Formation

Comparative studies60,93 with highly purified cytochromes P-450 1A2, 2B4 and 2E1 recombined with NADPH-cytochrome P-450 reductase and phospholipid revealed that the latter hemoprotein species catalyzed conversion of pyridine to its N-oxide with the largest turnover number (ca 5 min-1). It is interesting to note that P-450-enriched fractions, 

Detailed work has been devoted to the elucidation of factors governing N-oxygenation of amino azaheterocycles. To this end, a series of substituted 2,4-diaminopyrimidines and 6-aminopurines was subjected to metabolic analysis8,16,64,65,147,148 Generapy5 P-450 

FIGURE 3. Graphic displays of the cis and trims conformations of 9-benzyladenine (a) and variation of the potential energy of the azaheterocycle as a function of the torsion angles Z and r2 (b). Contours are shown at intervals of 1 kcalmol-1 with the lowest energy level (—17.6 kcal mol 1) indicated by the symbol (x). (Data taken from Ref. 148, with permission) 

Electron density at a particular endo -nitrogen and lipophilicity are other factors which may have an influence on the N-oxygenation of pyrimidines and purines by the P-450 system64,65,147,148. 

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