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The metabolism of toluene in human liver microsomes and by cDNA-expressed human cytochrome P450s (CYPs) was investigated. Toluene was metabolized mainly to benzyl alcohol and slightly to o- and p-cresol by human liver microsomes. Formation of o-cresol was elevated in microsomes from human livers derived from cigarette smokers, but the induced CYP isoforms were not clear. Of the eleven human CYP forms studied, CYP2E1 was the most active in forming benzyl alcohol, followed by CYP2B6, CYP2C8, CYP1A2, and CYP1A1, in that order. The activities of CYP2A6, CYP2C9, CYP2D6, CYP3A3, CYP3A4, and CYP3A5 were negligible. In addition, CYP2B6 and CYP2E1 catalyzed the formation of p-cresol (11-12% of total metabolites), and CYP1A2 catalyzed the formation of both o-(22%) and p-cresol (35%). The relationship between the amino acid sequence of rat CYP2B1 cDNA and the activity for toluene metabolism was investigated using variants, because of great differences in the forming of toluene ring products between CYP2B1 and CYP2B6. These results suggest that the structure of CYP2B1 at the site of Leu 58 rather than Ile-114 and Glu-282 plays an important role in the formation of toluene ring products, whereas in CYP2B1 Ile-114 plays an important role in the formation of benzyl alcohol. These results may explain, in part, the lower activity of CYP2B6, which has Phe at position 58 of the protein, for toluene ring oxidations than that of CYP2B1.
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E Elovaara, and
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O Pelkonen, and
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T Aoyama
January 1997,
European journal of clinical pharmacology,
T Nakajima, and
R S Wang, and
E Elovaara, and
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O Pelkonen, and
H Vainio, and
T Aoyama
December 1997,
Drug metabolism and disposition: the biological fate of chemicals,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
January 1994,
Chemical research in toxicology,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
November 1997,
Pharmacology,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
April 1997,
Drug metabolism and disposition: the biological fate of chemicals,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
September 2007,
Drug metabolism and disposition: the biological fate of chemicals,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
December 1999,
Pharmacology,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
April 1998,
Xenobiotica; the fate of foreign compounds in biological systems,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
January 1989,
Molecular carcinogenesis,
T Nakajima, and
R S Wang, and
E Elovaara, and
F J Gonzalez, and
H V Gelboin, and
H Raunio, and
O Pelkonen, and
H Vainio, and
T Aoyama
March 1999,
British journal of clinical pharmacology,
