cDNA cloning and expression of UDP-glucose dehydrogenase from bovine kidney

We have isolated a cDNA encoding UDP-glucose dehydrogenase from a bovine ki dney cDNA-library, the first mammalian cDNA clone published. [After submiss ion of the manuscript, a study appeared describing the molecular cloning an d characterization of the human and mouse UDP-glucose dehydrogenase genes ( Spicer ef al., 1998).] The enzyme catalyzes the conversion of UDP-glucose t o UDP-glucuronic acid, an essential precursor in glycosaminoglycan biosynth esis, The cDNA has an open reading frame of 1482 nucleotides coding for a 5 5 kDa protein. Expression of the enzyme in COS-7 cells showed a 3-fold incr ease in UDP-glucose dehydrogenase activity; also, the C-terminal 23 amino a cids was shown not to be necessary for enzyme activity. Northern blots from human and mouse tissues reveal high expression in liver and low in skeleta l muscle. Human tissues have a major transcript size of 3.2 kilobases and a minor of 2.6 whereas mouse tissues have a single 2.6 kilobase transcript. We have also developed a sensitive and direct assay using UDP-[C-14]Glc as a substrate for detection of small amounts of UDPGDH activity.