the UGTIA enzymes, the UGT2Al and 2A2 proteins have identical C-termini and

different N-termini that arise due to differential splicing of the first exon (Figure 2-4). By

contrast, the UGT2A3 gene comprises six exons that are not shared with the other two.

Table 2-1. Expression of human UGT mRNA in various tissues
UGT Liver Intestine Esophagus Kidney Brain Prostate Other tissues
 & stomach
1Al ///
1A3 J J Jb
1A4
1A6 J J Jb J testis, ovary
1A7 c
1A8
1A9
1A10c
2Al Olfactory
 epithelium, lung
2B4
2B7 Pancreas
2B10 mammary
 gland,
2B11 mammary
 gland, adrenal,
 skin, adipose
2B15 mammary
 gland, adipose,
 skin, lung,
 testis, uterus,
 placenta
2Bl7

a Tukey and Strassburg 2000; King et al., 2000; Lin and Wong 2002; Wells et al., 2004
b only a third of the population expresses these isoforms in gastric epithelium (Strassburg
et al., 1998)
c expressed in bile ducts