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4050805 
Journal Article 
Multiplicity of liver microsomal cytochrome P-450: separation, purification and characterization 
Lu, AY; Ryan, D; Kawalek, J; Thomas, P; West, SB; Huang, MT; Levin, W 
1976 
Yes 
Biochemical Society Transactions
ISSN: 0300-5127
EISSN: 1470-8752 
4 
1 
169-172 
English 
1001627 
The catalytic activity of a particular form of cytochrome P 450 cannot be predicted solely from the absorption maximum of its reduced CO difference spectrum. For example, rat cytochrome P 448 is 10 times better than rabbit cytochrome P 448 in supporting benzo[α]pyrene metabolism despite the similarity of their reduced CO difference spectra. One cannot classify the different forms of cytochrome P 450 according to the types of reaction catalysed by these enzymes. For example, the N dealkylation and O dealkylation of a compound might be catalysed by a single cytochrome P 450 or different forms of cytochrome P 450. Likewise, the hydroxylation of a compound at several different positions might be catalysed by one or several forms of cytochrome P 450. It is unlikely that a particular form of cytochrome P 450 can metabolize only a limited number of substrates. The substrate specificities of various forms of cytochrome P 450 appear to be broad and overlapping, although the rate of metabolism by different forms is different.