title: 6-methylhydroxylation of the anti-cancer agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) by flavin-containing monooxygenase 3.
abstract: The involvement of flavin-containing monooxygenase (FMO) in the 6-methylhydroxylation of the experimental anti-cancer drug 5,6-dimethylxanthenone-4-acetic acid (DMXAA) was investigated by use of human liver microsomes and microsomes containing cDNA-expressed FMOs. The involvement of FMO in the formation of 6-methyl hydroxylate of DMXAA, 6-hydroxymethyl-5-methylxanthenone-4-acetic acid (6-OH-MXAA) in human liver microsomes was indicated by the fact that this biotransformation was sensitive to heat treatment, increased at pH 8.3, and inhibited by methimazole. Only FMO3 formed 6-OH-MXAA at a similar rate to that in cDNA-expressed cytochromes P-450 (CYP)1A2. The results of this study indicate that human FMO3 has the capacity to form 6-OH-MXAA, but plays a lesser important role for this reaction than CYP1A2 that has been demonstrated to catalyse 6-OH-MXAA formation.
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism*; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D006801:Humans; D006900:Hydroxylation; D008862:Microsomes, Liver / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism*; D014966:Xanthenes / Q000737:chemistry / Q000378:metabolism*; D044004:Xanthones
chemical_list: D000970:Antineoplastic Agents; D014966:Xanthenes; D044004:Xanthones; C066668:vadimezan; D006899:Mixed Function Oxygenases; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D019388:Cytochrome P-450 CYP1A2