Comparative Studies of the Indoleamine Dioxygenase-like Myoglobin from the Abalone Sulculus diversicolor

• Published in: Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology Vol. 117; no. 4; pp. 599 - 604
• Main Authors: Suzuki, Tomohiko, Imai, Kiyohiro
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01.08.1997
• Subjects: Amino Acid Sequence; Animals; Conserved Sequence; convergent evolution; Hemoglobin; indoleamine dioxygenase; Indoleamine-Pyrrole 2,3,-Dioxygenase; Marine; Molecular Sequence Data; Mollusca - chemistry; myoglobin; Myoglobin - chemistry; Myoglobin - genetics; Myoglobin - metabolism; Oxygen - metabolism; oxygen equilibrium; Phylogeny; Saccharomyces - chemistry; sequence homology; Sequence Homology, Amino Acid; Sulculus diversicolor; Temperature; Tryptophan Oxygenase - chemistry; Tryptophan Oxygenase - metabolism; Whales; indoleamine dioxygenase; sequence homology; Sulculus diversicolor; convergent evolution; Hemoglobin; oxygen equilibrium; myoglobin
• ISSN: 1096-4959; 0305-0491; 1879-1107
• DOI: 10.1016/S0305-0491(97)00017-5

The abalone Sulculus diversicolor contains abundant myoglobin in its buccal mass. The myoglobin is homodimeric and the molecular mass of the constituent polypeptide chain is 41,000 Da. The amino acid sequence and gene structure are highly homologous with those of a vertebrate tryptophan-degrading enzyme, indoleamine dioxygenase (IDO). Thus Sulculus myoglobin evolved from an IDO gene, and represents a typical case of functional convergence. The oxygen equilibrium properties of Sulculus myoglobin were examined and compared with those of myoglobins from other sources. It binds oxygen reversibly, and the P50 was determined to be 3.8 mmHg at 20°C and pH 7.4, showing that the oxygen affinity of Sulculus myoglobin is significantly lower than those of usual 16 kDa myoglobins. It also displays no cooperativity (nmax: 1.02–1.06) and no alkaline Bohr effect between pH 7.0 and 7.9. The cDNA-derived amino acid sequences of vertebrate IDOs, molluscan IDO-like myoglobins and a homolog in the yeast Saccharomyces were aligned, and several amino acid residues were proposed as candidates for key residues to control the function of IDO or myoglobin.