Intronic polymorphisms of cytochromes P450.
The cytochrome P450 enzymes active in drug metabolism are highly polymorphic. Most allelic variants have been described for enzymes encoded by the cytochrome P450 family 2 (CYP2) gene family, which has 252 different alleles. The intronic polymorphisms in the cytochrome P450 genes account for only a small number of the important variant alleles; however, the most important ones are CYP2D6*4 and CYP2D6*41 , which cause abolished and reduced CYP2D6 activity, respectively, and CYP3A5* 3 and CYP3A5*5 , common in Caucasian populations, which cause almost null activity. Their discoveries have been based on phenotypic alterations within individuals in a population, and their identification has, in several cases, been difficult and taken a long time. In light of the next-generation sequencing projects, it is anticipated that further alleles with intronic mutations will be identified that can explain the hitherto unidentified genetic basis of inter-individual differences in cytochrome P450-mediated drug and steroid metabolism.
Ingelman-Sundberg
Magnus
M
Section of Pharmacogenetics, Department of Physiology and Pharmacology, Karolinska Institutet, SE-17177 Stockholm, Sweden. magnus.ingelman-sundberg@ki.se
Sim
Sarah C
SC
D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D051544:Cytochrome P-450 CYP3A / Q000235:genetics*; D006801:Humans; D007438:Introns / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*
C510164:CYP3A5 protein, human; D019389:Cytochrome P-450 CYP2D6; D051544:Cytochrome P-450 CYP3A