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
• 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 benzoapyrene (BaP), has several genetic variants. This study investigated six rare mutations and four common polymorphisms for their effects on BaP metabolism. Five missense mutations associated with congenital glaucoma (Gly61Glu, Gly365Trp, Asp374Asn, Pro437Leu and Arg469Tryp) dramatically decreased the capacity of CYP1B1 to convert (-)benzoapyrene-7R-trans-7,8-dihyrodiol (BaP-7,8-diol) to (+/-)benzoapyrene-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 BaP-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 BaP-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:
  • Metabolism
  • Genes
  • Genetics
  • Enzymology
  • Humans
  • Mutagenesis
  • Mutation
  • Oxidation
  • Oxidation-reduction-reactions
• ISSN:
  0143-3334
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  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)
• Topic:
  Workplace Safety & Health
• Location:
  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
• Download URL:
  https://stacks.cdc.gov/view/cdc/191893/cdc_191893_DS1.pdf
• File Type:
  [PDF - 176.61 KB]
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:25fb2c7a67c4eb2568a5bbf42e6e3f5837172aef3888715de80ddef9dd27af2e1a7dd2c064f1a1d550dfbdb5cdb3b8bf9cc3be917e273cef0e7ff493a54ecc4b