Table 1. Polymorphisms in phase I and phase II drug metabolizing enzymes.
| Enzyme | Genotype | Phenotype |
|---|---|---|
| cytochrome P450 | ||
| CYP2C9 | *1/*1 | extensive metabolizer |
| CYP2C19 | *1/*2 | poor metabolizer |
| CYP2D6 | *1/*4 | extensive metabolizer |
| N-acetyltransferase | ||
| NAT1 | *4/*4 | normal activity |
| NAT2 | *5B/*5B | catalytically inefficient |
| glutathione S-transferase | ||
| GSTM1 | *0/*0 | no activity |
| GSTT1 | *0/*0 | no activity |
| GSTP1 | *A/*A | normal activity |
Genotyping results for drug metabolizing enzymes: In cytochrome P450 nomenclature the gene name and allele are separated by an asterisk, and the number 1 is given to the wild-type version of the gene. CYP2C9*1/*1 encodes wild-type CYPC2C9. NAT1*4/*4 encodes a wild-type isoenzyme with normal catalytic activity. In GST nomenclature *0 represents a complete gene deletion, and individuals who are homozygous for the *0 allele (null genotype) lack any functional GST protein. GSTP1*A /*A encodes functional wild-type GSTP1. Cytochrome P450 polymorphisms were identified by DA Flockhart, Indiana University School of Medicine, Indianapolis, IN, N-acetyltransferase polymorphisms by PK Knoefel, University of Louisville School of Medicine, Louisville, KY, and glutathione S-transferase polymorphisms in collaboration with M-A Loriot, Hôpital Européen Georges Pompidou, Paris, France.