title: Metabolic activation of polycyclic aromatic hydrocarbon trans-dihydrodiols by ubiquitously expressed aldehyde reductase (AKR1A1).
abstract: Polycyclic aromatic hydrocarbons (PAHs) are metabolized to trans-dihydrodiol proximate carcinogens by CYP1A1 and epoxide hydrolase (EH). CYP1A1 or aldo-keto reductases (AKRs) from the 1C subfamily can further activate the trans-dihydrodiols by forming either anti-diol-epoxides or reactive and redox active o-quinones, respectively. To determine whether other AKR superfamily members can divert trans-dihydrodiols to o-quinones, the cDNA encoding human aldehyde reductase (AKR1A1) was isolated from hepatoma HepG2 cells using RT-PCR, subcloned into a prokaryotic expression vector, overexpressed in E. coli and purified to homogeneity in milligram amounts. Studies revealed that AKR1A1 preferentially oxidized the metabolically relevant (-)-[3R,4R]-dihydroxy-3,4-dihydrobenz[a]anthracene. AKR1A1 also displayed high utilization ratios (V(max)/K(m)) for the following PAH trans-dihydrodiols: (+/-)trans-3,4-dihydroxy-3,4-dihydro-7-methylbenz[a]anthracene, (+/-)trans-3,4-dihydroxy-3,4-dihydro-7,12-dimethylbenz[a]anthracene and (+/-)trans-7,8-dihydroxy-7,8-dihydro-5-methylchrysene. Multiple tissue expression (MTE) arrays were used to measure the co-expressed of CYP1A1, EH and AKR1A1. All the three enzymes co-expressed to sites of PAH activation. The high catalytic efficiency of AKR1A1 for potent proximate carcinogen trans-dihydrodiols and its presence in tissues that contain CYP1A1 and EH suggests that it plays an important role in this alternative pathway of PAH activation (supported by CA39504).
authors: Departments of Biochemistry and Biophysics, and Pharmacology, University of Pennsylvania School of Medicine, 3620 Hamilton Walk, 19104-6084, Philadelphia, PA, USA.
authors: N T
authors: NT
authors: Palackal
authors: M E
authors: ME
authors: Burczynski
authors: R G
authors: RG
authors: Harvey
authors: T M
authors: TM
authors: Penning
mesh_terms: D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism*; D001711:Biotransformation; D002460:Cell Line; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D004851:Epoxide Hydrolases / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D006801:Humans; D066298:In Vitro Techniques; D010084:Oxidation-Reduction; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013237:Stereoisomerism
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D011994:Recombinant Proteins; D000449:Aldehyde Reductase; D019363:Cytochrome P-450 CYP1A1; D004851:Epoxide Hydrolases