Rat small intestine expresses primarily type VI gamma-glutamyl transpeptidase RNA

To clarify differences between gamma-glutamyl transpeptidase (gamma GT) expression in the rat and the mouse small intestine, we cloned and sequenced 13 rat small intestine gamma GT cDNAs and compared them with those obtained from the mouse (Carter, et al. (1994) J. Biol. Chem. 269, 24581-24585). We found that all 13 were type VI, which in both species accounts for 80-90% of intestinal gamma GT. However, rat type VI gamma GT is substantially longer than mouse type VI RNA and includes at least 67 additional nucleotides at the 5' end that are non-homologous with the 5' end of the mouse type VI RNA; further, these show no homology to another mouse exon (VII) that splices to type VI RNA. In addition, a 168 nucleotide stretch is present in the middle of rat RNA that is absent in mouse type VI RNA.