Single amino acid mutations, but not common polymorphisms, decrease the activity of CYP1B1 against (-)benzo[a]pyrene-7R-trans-7,8-dihydrodiol

Details

• Personal Author:
  Abou-Zahr F ; Bejjani BA ; Bell DA ; Li Y ; Mammen JS ; Pittman GS ; Strickland PT ; Sutter TR ; Abou-Zahr F ; Bejjani BA ; Bell DA ; Li Y ; Mammen JS ; Pittman GS ; Strickland PT ; Sutter TR
• Description:
  Genetic differences that underlie inter-individual variation in the metabolism of common carcinogens are important potential sources of cancer susceptibility. Cytochrome P450 1B1 (CYP1B1), a central enzyme in the activation of the ubiquitous environmental carcinogen benzo[a]pyrene (B[a]P), has several genetic variants. This study investigated six rare mutations and four common polymorphisms for their effects on B[a]P metabolism. Five missense mutations associated with congenital glaucoma (Gly61Glu, Gly365Trp, Asp374Asn, Pro437Leu and Arg469Tryp) dramatically decreased the capacity of CYP1B1 to convert (-)benzo[a]pyrene-7R-trans-7,8-dihyrodiol (B[a]P-7,8-diol) to (+/-)benzo[a]pyrene-r-7,t-8-dihydrodiol-9,10-epoxides. These five mutations resulted in enzymes with 3-12% of normal activity when assayed in vitro using an Saccharomyces cerevisiae microsomal expression system. A 10 bp deletion mutation produced no detectable protein or activity. In contrast, proteins containing all possible combinations of four common single nucleotide polymorphisms (Arg48Gly, Ala199Ser, Val432Leu, Asn453Ser) had modest effects on B[a]P-7,8-diol metabolism. Michaelis-Menten analysis suggested that two alleles, Arg48, Ala119, Val432, Ser453 (RAVS) and Arg48, Ala119, Leu432, Ser453 (RALS), have KM values 2-fold lower than Arg48, Ala119, Val432, Ser453 (RAVN): 1.4+/-0.3 and 1.3+/-0.4 microM, respectively, compared with 2.8+/-0.8 microM (P<0.05). However, these differences could not be confirmed with direct measurements of rate at low substrate concentration. There were no significant differences for either of two other kinetic parameters, kcat or kcat/KM. Allele frequency analysis in three populations reveals the Ser453 variant is rare among those of Asian (<1%) and African ancestry (<4%), and more common in individuals of European ancestry (16%). Haplotypes containing the Ser453 variant were uncommon; only RALS was detectable in our small populations. The RALS allele occurred between 0.5% in Asians and 15% in Europeans. Our study demonstrates that rare, disease-associated mutations in CYP1B1 significantly decrease the enzyme's metabolism of B[a]P-7,8-diol; however, our results do not identify any major differences in this metabolism due to four common single amino acid polymorphisms. [Description provided by NIOSH]
• Subjects:
  Energy Metabolism Genetics Mutagens Occupational Health Safety
• Keywords:
  Enzymology Genes Humans Metabolism Mutagenesis Mutation Oxidation Oxidation-reduction-reactions
• ISSN:
  0143-3334
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article ; Journal Article
• Place as Subject:
  Maryland ; North Carolina ; OSHA Region 3 ; OSHA Region 4 ; OSHA Region 6 ; Tennessee ; Texas
• CIO:
  National Institute for Occupational Safety and Health (NIOSH) ; National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health ; Workplace Safety & Health
• Location:
  North America ; North America
• Volume:
  24
• Issue:
  7
• NIOSHTIC Number:
  nn:20038066
• Citation:
  Carcinogenesis 2003 Jul; 24(7):1247-1255
• Contact Point Address:
  Paul T.Strickland, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe St, Baltimore, MD 21205
• Email:
  pstrickl@jhsph.edu
• Federal Fiscal Year:
  2003
• Performing Organization:
  Johns Hopkins University
• Peer Reviewed:
  True
• Start Date:
  20050701
• Source Full Name:
  Carcinogenesis
• End Date:
  20280630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:25fb2c7a67c4eb2568a5bbf42e6e3f5837172aef3888715de80ddef9dd27af2e1a7dd2c064f1a1d550dfbdb5cdb3b8bf9cc3be917e273cef0e7ff493a54ecc4b
• Download URL:
  https://stacks.cdc.gov/view/cdc/191893/cdc_191893_DS1.pdf
• File Type:
  [PDF - 176.61 KB ]