HUMAN CYSTEINE DIOXYGENASE TYPE-I - PRIMARY STRUCTURE DERIVED FROM BASE SEQUENCING OF CDNA

The base sequence of cDNA encoding the complete human liver cysteine d ioxygenase type I (CDO-I; EC 1.13.11.20) message, and the derived amin o-acid sequence are reported. CDO-I is encoded on a single mRNA specie s (approx. 1.5 kb). Human CDO-I clones were identified by screening a liver cDNA library, and inserts were isolated and sequenced. In additi on, human liver total RNA was reverse-transcribed and CDO-I cDNA ampli fied by PCR using a modified poly-T primer and specific CDO-I primers to give a second source of sequencing template. The CDO-I message enco des a 200 amino-acid residue protein, the sequence of which has greate r than 90% homology with the equivalent rat enzyme. The message was no t expressed in a human hepatoma cell line (Hep G2).