title: Molecular characterization of adenosine 5'-monophosphate deaminase--the key enzyme responsible for the umami taste of nori (Porphyra yezoensis Ueda, Rhodophyta).
abstract: The enzyme adenosine 5'-monophosphate deaminase (AMPD, EC 3.5.4.6) catalyzes the conversion of adenosine 5'-monophosphate to inosine 5'-mononucleotide (IMP). IMP is generally known as the compound responsible for the umami taste of the edible red alga Porphyra yezoensis Ueda that is known in Japan as nori. Therefore, we suspect that AMPD plays a key role in providing a favorable nori taste. In this study, we undertake the molecular characterization of nori-derived AMPD. The nori AMPD protein has a molecular mass of 55 kDa as estimated from both gel filtration and sodium dodecyl sulfate polyacrylamide gel electrophoresis. The calculated molecular mass from the amino acid sequence deduced from cDNA is 57.1 kDa. The isoelectric point is 5.71. The coding region of AMPD consists of 1,566 bp encoding 522 amino acids and possesses a transmembrane domain and two N-glycosylation sites. The sequence identity of nori AMPD in human and yeast AMPDs was found to be less than 50% and 20% in DNA and amino acid sequences, respectively. Proline in the conserved motif of [SA]-[LIVM]-[NGS]-[STA]-D-D-P was found to be converted to glutamate. These results indicate that nori AMPD is a novel type of AMPD.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai, Miyagi 985-8555, Japan.
authors.forename: Seiko
authors.initials: S
authors.lastname: Minami
authors.forename: Minoru
authors.initials: M
authors.lastname: Sato
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Shiraiwa
authors.forename: Koji
authors.initials: K
authors.lastname: Iwamoto
mesh_terms: D000659:AMP Deaminase / Q000235:genetics* / Q000302:isolation & purification; D000595:Amino Acid Sequence; D001483:Base Sequence; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D007292:Inosine Nucleotides / Q000737:chemistry*; D008969:Molecular Sequence Data; D044664:Porphyra / Q000201:enzymology*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013649:Taste
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D007292:Inosine Nucleotides; D000659:AMP Deaminase