CLONING AND SEQUENCING OF A CDNA-ENCODING RAT D-DOPACHROME TAUTOMERASE

An enzyme which converts D-dopachrome into 5,6-dihydroxyindole has recently been isolated from rat liver, Enzymatic D-dopachrome conversion has been observed in extracts from all tissues examined of several species, including man, We have now cloned and sequenced a 628 bp long cDNA encoding the enzyme provisionally called D-dopachrome tautomerase, The cDNA was isolated by 3' and 5' rapid amplification and cloning of cDNA ends (RACE) from rat liver cells using degenerate oligonucleotide primers, deduced from the IV-terminal peptide sequence of D-dopachrome tautomerase. The cDNA contains an open reading frame encoding 118 amino acids. Edman degradation of intact and of trypsin degraded D-dopachrome tautomerase fragments gave information on and corroborated 67% of the deduced protein sequence, A homology search in the EST database found a human cDNA encoding a peptide sharing 66% homology with the rat enzyme, The rat D-dopachrome tautomerase shares 27% homology with the rat macrophage migration inhibitory factor (MIF).