Cloning and sequencing of a cDNA encoding rat d‐dopachrome tautomerase

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Abstract
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 N‐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).