Characterization and substrate specificity of UGT2B4 (E-458): a UDP-glucuronosyltransferase encoded by a polymorphic gene

Variations in glucuronidation activities among different individuals have b een reported; however, genetic polymorphisms in the genes encoding phase II drug metabolizing UDP-glucuronosyl-transferases have not been studied exte nsively. A novel UGT2B cDNA clone UGT2B4(E-458) was isolated from human pro state and LNCaP cell cDNA libraries. The cDNA encoding UGT2B4(E-458) is 209 7 bp in length and has an open reading frame of 1584 nucleotides encoding a protein of 528 amino acids, Characterization of the UGT2B4 (E-458) cDNA re vealed nucleotide differences with the previously published UGT2B4 and UGT2 B11 cDNAs. These variations in the UGT2B4 sequence lead to an amino acid ch ange from aspartic acid to glutamic acid at position 458. In the previous U GT2B11 cDNA (which has subsequently been renamed UGT2B4 (L-109,L-396, D-458 )), leucine residues are found at positions 109 and 396, whereas phenylalan ines are present at these positions in the UGT2B4(D-458) and UGT2B4(E-458) enzymes. Analysing the genomic DNA of 26 unrelated Caucasian individuals de monstrated the presence of variant alleles encoding UGT2B4(D-458) and UGT2B 4 (E-458). Stable expression of UGT2B4(E-458) cDNA in HK293 cells demonstra tes the presence of a 52 kDa protein, which is in agreement with other char acterized UGT2B proteins, UGT2B4 (E-458) conjugates hyodeoxycholic acid (HD CA) as well as 4-hydroxyestrone (4-OH-E1), androstane-3 alpha,17 beta-diol (3 alpha-diol) and androsterone (ADT), Specific reverse transcriptase - pol ymerase chain reaction analysis revealed expression of UGT2B4(D-458) and UG T2B4(E-458) transcripts in a wide range of extrahepatic tissues, including the liver, kidney, testis, mammary gland, prostate, placenta, adipose, adre nal, shin and lung, Our results suggest that UGT2B4(E-458) and UGT2B(E458) are two widely expressed isoenzymes, and that polymorphism in the UGT2B4 ge ne might be responsible for differences in UGT2B4 enzymatic properties. Pha rmacogenetics 9:207-216 (C) 1999 Lippincott Williams & Wilkins.