Publications

• NMR characterization of physicochemical properties of rat D-dopachrome tautomerase.

  Yoshida H., Nishihira J., Suzuki M., Hikichi K.

  D-dopachrome tautomerase (DOPD) catalyzes the conversion of D-dopachrome to 5,6-dihydroxyindole. DOPD was found to have amino acid sequence homology with macrophage migration inhibitor factor (MIF), suggesting that DOPD functions as a proinflammatory cytokine. We here demonstrate the physicochemic ... >> More

  D-dopachrome tautomerase (DOPD) catalyzes the conversion of D-dopachrome to 5,6-dihydroxyindole. DOPD was found to have amino acid sequence homology with macrophage migration inhibitor factor (MIF), suggesting that DOPD functions as a proinflammatory cytokine. We here demonstrate the physicochemical properties of DOPD by nuclear magnetic resonance (NMR). The native molecular weight of rat DOPD was about 37 kDa as calculated from Sephadex G-100 column chromatography. Since the deduced molecular weight of its cDNA (117 amino acid residues) is 12.5 kDa, it is assumed that DOPD exists as a homotrimer in native form. Since several methyl proton resonances were observed in the high magnetic field region of the one-dimensional 1H-NMR spectrum, DOPD appeared to have a hydrophobic core in which methyl groups and aromatic groups are located close to each other. From a simple integration of one-dimensional 1H-NMR spectra, the contents of the alpha-helix, beta-strand, and random coil were calculated to be 16%, 68%, and 16%, respectively. Since the denaturation temperature of DOPD is exceedingly high at the range between 90-100 degrees C, it is considered that the high beta-strand content may contribute to its heat stability. << Less

  Biochem Mol Biol Int 42:891-899(1997) [PubMed] [EuropePMC]

• Isolation of a new tautomerase monitored by the conversion of D-dopachrome to 5,6-dihydroxyindole.

  Odh G., Hindemith A., Rosengren A.-M., Rosengren E., Rorsman H.

  Two membrane bound enzymes which tautomerize L-dopachrome and are specific for the L-isomer of dopachrome have been defined in melanin forming cells. Another enzyme that tautomerizes D-dopachrome with concomitant decarboxylation to give 5,6-dihydroxyindole (DHI) was found in the cytoplasm of human ... >> More

  Two membrane bound enzymes which tautomerize L-dopachrome and are specific for the L-isomer of dopachrome have been defined in melanin forming cells. Another enzyme that tautomerizes D-dopachrome with concomitant decarboxylation to give 5,6-dihydroxyindole (DHI) was found in the cytoplasm of human melanoma cells, human liver and in all of the organs studied in rat. The decolorization of D-dopachrome with the formation of DHI was used in monitoring the isolation of a tautomerase from liver of male rats and therefore the enzyme is provisionally called D-dopachrome tautomerase. The molecular weight of D-dopachrome tautomerase monomer was approximately 12 kD and its N-terminal amino acid sequence was P-F-V-E-L-E-T-N-L-P-A-. The Km for D-dopachrome was 1.5 mM and Vmax 0.5 mmol per min and mg protein. << Less

  Biochem. Biophys. Res. Commun. 197:619-624(1993) [PubMed] [EuropePMC]

• Molecular cloning of human D-dopachrome tautomerase cDNA: N-terminal proline is essential for enzyme activation.

  Nishihira J., Fujinaga M., Kuriyama T., Suzuki M., Sugimoto H., Nakagawa A., Tanaka I., Sakai M.

  D-Dopachrome tautomerase converts 2-carboxy-2,3-dihydroindole-5,6-quinone (D-dopachrome) into 5,6-dihydroxyindole. This protein has an amino acid sequence that is highly homologous with that of macrophage migration inhibitory factor (MIF), which has the potential to catalyze D-dopachrome to 5,6-di ... >> More

  D-Dopachrome tautomerase converts 2-carboxy-2,3-dihydroindole-5,6-quinone (D-dopachrome) into 5,6-dihydroxyindole. This protein has an amino acid sequence that is highly homologous with that of macrophage migration inhibitory factor (MIF), which has the potential to catalyze D-dopachrome to 5,6-dihydroxyindole-2-carboxylic acid and is an important cytokine for T-lymphocyte activation. We isolated and sequenced a 566 bp-long cDNA encoding human D-dopachrome tautomerase. The cDNA contains an open reading frame encoding 118 amino acids, including the initiator methionine. The amino acid sequence of the protein shares 80% homology with that of the rat enzyme. Northern blot analysis demonstrated that mRNA of D-dopachrome tautomerase is expressed in a large amount in the liver, and to lesser extent in other organs, including the heart, lung and pancreas. After purification of D-dopachrome tautomerase expressed in E. coli, we confirmed that the recombinant protein catalyzes the conversion of D-dopachrome to 5,6-dihydroxyindole. Its catalytic mechanism is not well understood. We found that the protein completely lost the enzyme activity when the N-terminal proline residue was replaced with alanine by site-directed mutagenesis. This fact suggests that the N-terminal proline is essential for the catalytic mechanism. Although the precise pathophysiological function of D-dopachrome tautomerase remains to be elucidated, the present results could contribute to further understanding of isomerase activity in relation to the immune response. << Less

  Biochem. Biophys. Res. Commun. 243:538-544(1998) [PubMed] [EuropePMC]

• Crystal structure of human D-dopachrome tautomerase, a homologue of macrophage migration inhibitory factor, at 1.54-A resolution.

  Sugimoto H., Taniguchi M., Nakagawa A., Tanaka I., Suzuki M., Nishihira J.

  D-Dopachrome tautomerase shares a low homologous amino acid sequence (33% homology) with the macrophage migration inhibitory factor (MIF) and possesses similar tautomerase activity as well. MIF is a cytokine involved in inflammatory reactions and immune responses. Whereas recent studies have ident ... >> More

  D-Dopachrome tautomerase shares a low homologous amino acid sequence (33% homology) with the macrophage migration inhibitory factor (MIF) and possesses similar tautomerase activity as well. MIF is a cytokine involved in inflammatory reactions and immune responses. Whereas recent studies have identified MIF as a pituitary hormone and immunoregulator, much less is known about the structural basis of these physiological functions and the real significance of tautomerase activity. Therefore, interest in the structure-function relationship between D-dopachrome tautomerase and MIF has increased, especially with regard to inflammation and immune responses. We have determined the X-ray crystal structure of human D-dopachrome tautomerase at 1.54 A resolution. D-Dopachrome tautomerase folds to form a homotrimer that has extensive contact between subunits by intersubunit beta-sheets. Its overall topology and trimeric formations are similar to those of human MIF. The N-terminal proline is located at the bottom of a positively charged pocket in which the conformations of Lys32 and Ser63 are highly conserved. These positively charged properties are also seen in the active site pocket of human MIF, bacterial 5-(carboxymethyl)-2-hydroxymuconate isomerase (CHMI), and 4-oxalocrotonate tautomerase (4-OT). A detailed comparison of these structures revealed significant differences in the environment around the potential active site, the intersubunit contacts, and charge distribution on the molecular surface. It can be concluded that these features are related to the physiological role and tautomerase activity of MIF and D-dopachrome tautomerase. The present structural study could be helpful for designing effective inhibitors that modulate immunoregulatory and hormone-like effects. << Less

  Biochemistry 38:3268-3279(1999) [PubMed] [EuropePMC]