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

An enzyme which converts D-dopachrome into 5,6-dihydroxyindole has rec ently been isolated from rat liver, Enzymatic D-dopachrome conversion has been observed in extracts from all tissues examined of several spe cies, including man, We have now cloned and sequenced a 628 bp long cD NA 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-dopachrom e tautomerase. The cDNA contains an open reading frame encoding 118 am ino acids. Edman degradation of intact and of trypsin degraded D-dopac hrome tautomerase fragments gave information on and corroborated 67% o f the deduced protein sequence, A homology search in the EST database found a human cDNA encoding a peptide sharing 66% homology with the ra t enzyme, The rat D-dopachrome tautomerase shares 27% homology with th e rat macrophage migration inhibitory factor (MIF).