Comparison of substrate metabolism by wild type CYP2D6 protein and a variant containing methionine, not valine, at position 374

Pharmacogenetics. 1995 Aug;5(4):234-43. doi: 10.1097/00008571-199508000-00007.


We have analysed kinetic parameters of cDNA-derived CYP2D6 proteins derived from the original CYP2D6 cDNA isolate (Gonzalez FJ et al. Nature 1988: 331, 442-446) which contains methionine at position 374 (CYP2D6-Met) and a modified cDNA which contains valine at position 374 (CYP2D6-Val). This latter protein is predicted from the CYP2D6 genomic sequence. Several quantitative differences, but no qualitative differences in metabolism were observed. CYP2D6-Met was found to have a two-fold lower Km and a three-fold lower turnover rate for (R)(+)-bufuralol 1'-hydroxylation as compared to CYP2D6-Val. In contrast, CYP2D6-Met and CYP2D6-Val had a similar Km for debrisoquine 4-hydroxylation while CYP2D6-Val had an 18-fold higher turnover rate. CYP2D6-Val and CYP2D6-Met had similar Kms for metoprolol but CYP2D6-Val showed a three-fold higher capacity for the O-demethylation reaction compared to alpha-hydroxylation which is more similar to that seen in human liver. In the case of sparteine, CYP2D6-Val and CYP2D6-Met showed similar capacities for formation of the 2-dehydrosparteine metabolite but the Km value for CYP2D6-Met was six-fold higher than that for CYP2D6-Val. Kinetic differences between CYP2D6-Met and CYP2D6-Val were further probed by examination of apparent Ki for inhibition of (R,S)(+/-)-bufuralol 1'-hydroxylation. Similar Ki values (within a factor of three) were observed for perhexiline and (R,S)-propranolol while quinidine and dextromethorphan were 8.5-fold and 21-fold more effective inhibitors of CYP2D6-Val relative to CYP2D6-Met. An allele specific polymerase chain reaction assay was developed for the CYP2D6-Met allele. The CYP2D6-Met allele was not found among 83 individuals. In the aggregate, these data indicated that the CYP2D6-Val allele is the more common allele in human populations. The quantitative kinetic differences between these two enzymes appears most pronounced for substrates/inhibitors with rigid structures. CYP2D6-Val more often has a substantially lower Km and/or a substantially higher capacity to metabolize those substrates.

Publication types

  • Comparative Study

MeSH terms

  • B-Lymphocytes
  • Base Sequence
  • Cell Line
  • Cytochrome P-450 CYP2D6
  • Cytochrome P-450 Enzyme System / biosynthesis
  • Cytochrome P-450 Enzyme System / genetics*
  • Cytochrome P-450 Enzyme System / metabolism*
  • DNA Primers
  • DNA, Complementary
  • Dexamethasone / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Genetic Variation*
  • Humans
  • Kinetics
  • Methionine*
  • Microsomes / enzymology
  • Mixed Function Oxygenases / biosynthesis
  • Mixed Function Oxygenases / genetics*
  • Mixed Function Oxygenases / metabolism*
  • Molecular Sequence Data
  • Point Mutation
  • Polymerase Chain Reaction
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / metabolism
  • Restriction Mapping
  • Substrate Specificity
  • Transfection
  • Valine*


  • DNA Primers
  • DNA, Complementary
  • Enzyme Inhibitors
  • Recombinant Proteins
  • Dexamethasone
  • Cytochrome P-450 Enzyme System
  • Methionine
  • Mixed Function Oxygenases
  • Cytochrome P-450 CYP2D6
  • bufuralol 1'-hydroxylase
  • Valine