Details

Autor(en) / Beteiligte

• Veronese, Maurice E.
• Mackenzie, Peter I.
• Doecke, Christopher J.
• McManus, Michael E.
• Miners, John O.
• Birkett, Donald J.

Titel

Tolbutamide and phenytoin hydroxylations by cDNA-expressed human liver cytochrome P4502C9

Ist Teil von

• Biochemical and biophysical research communications, 1991-03, Vol.175 (3), p.1112-1118

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

1991

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• A human cytochrome P4502C9 cDNA clone has been isolated from a human liver bacteriophage Lambda gt11 library using oligonucleotide probes. Expression of the 1762 base pair cDNA in COS cells demonstrated that the encoded enzyme has a molecular mass of 55 kDa as determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The expressed enzyme catalysed the methylhydroxylation of tolbutamide with an apparent K m of 131.7 μM, similar to that observed in human liver microsomes. P4502C9 also catalysed the 4-hydroxylation of phenytoin, and inhibition experiments demonstrated that phenytoin was a competitive inhibitor of tolbutamide hydroxylation with an apparent K i of 19.1 μM. Sulphaphenazole was a potent inhibitor of the expressed enzyme with respect to both tolbutamide and phenytoin hydroxylations. These data demonstrate that a single isozyme can catalyse the hydroxylations of both tolbutamide and phenytoin, and suggest that both reactions are mediated by the same isozyme(s) of cytochrome P450 in human liver.