Four distinct membrane bound dipeptidase rnas are differentially expressed in the mouse

Membrane bound dipeptidase (MBD) is responsible for the breakdown of GSH by cleaving the cysteinyl glycine bond after a gamma glutamyl group is removed by gamma glutamyl transpeplidase (GOT). We have studied MBD RNA expression in different mouse tissues using cDNA cloning, nuclease protection, and northern analysis and found that at least four distinct RNA species exist. These arise as a result of transcription from two promoters and the use of two different poly A addition sites. MBD RNA expression is high in intestine, kidney, and lung. Type I RNAs are expressed primarily in small intestine and kidney, while type II RNAs are utilized in lung and kidney. Genomic cloning reveals that the mouse gene spans 17 kb and consists of 11 exons. The two promoters are located about 6 kb apart on the gene. MBD and GGT are both expressed at high levels in kidney and intestine. While MBD is expressed at high levels in the lung, GGT is almost undetectable. The reverse is true in the seminal vesicles. Thus, although MBD and GGT may act in concert to metabolize GSH in some tissues, they appear to function independently in other tissues.