Hepatic localisation of rat cysteine dioxygenase

Background/Aim: Cystein dioxygenase (CDO, E.C. 1.13.11.20) is the main catabolic enzyme of cysteine, metabolising cystein to cysteinesulphinic acid. CDO abnormality has been implicated in a number of neurologic and non-neurological diseases, with CDO deficiency possibly leading to excitotoxic damage to the brain and impaired Phase II metabolism in the liver. Methods: Two novel anti-CDO antibodies raised against linear synthetic peptides corresponding to two distinct epitopes on the 22 kDa gene product of the CDO-I gene were used for immunohistochemistry and Western blotting. These antibodies were characterised by their ability to both block and precipitate CDO enzyme activity as well as the ability of the respective antigenic peptides to absorb the antibodies and prevent the immunodetection of CDO. Results: The antibodies were found to detect the presence of a 68 kDa protein, which was subsequently shown to be CDO. Distribution was found to be centrilobular and did not alter when CDO was induced with cysteine or methionine; however, the intensity of staining increased, indicating an increase in the levels of CDO in that region. Conclusion: These results suggest that the 68 kDa Type II is the predominant isoform in vitro and in vivo and that is centrilobular localisation may allow CDO to initate the production of sulphate and taurine for Phase II conjugation in the liver.