title: Microbial production of sensory-active miraculin.
abstract: Miraculin (MCL), a tropical fruit protein, is unique in that it has taste-modifying activity to convert sourness to sweetness, though flat in taste at neutral pH. To obtain a sufficient amount of MCL to examine the mechanism involved in this sensory event at the molecular level, we transformed Aspergillus oryzae by introducing the MCL gene. Transformants were expressed and secreted a sensory-active form of MCL yielding 2 mg/L. Recombinant MCL resembled native MCL in the secondary structure and the taste-modifying activity to generate sweetness at acidic pH. Since the observed pH-sweetness relation seemed to reflect the imidazole titration curve, suggesting that histidine residues might be involved in the taste-modifying activity. H30A and H30,60A mutants were generated using the A. oryzae-mediated expression system. Both mutants found to have lost the taste-modifying activity. The result suggests that the histidine-30 residue is important for the taste-modifying activity of MCL.
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Ito
authors.forename: Tomiko
authors.initials: T
authors.lastname: Asakura
authors.forename: Yuji
authors.initials: Y
authors.lastname: Morita
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Nakajima
authors.forename: Ayako
authors.initials: A
authors.lastname: Koizumi
authors.forename: Akiko
authors.initials: A
authors.lastname: Shimizu-Ibuka
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Masuda
authors.forename: Masaji
authors.initials: M
authors.lastname: Ishiguro
authors.forename: Tohru
authors.initials: T
authors.lastname: Terada
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Maruyama
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamoto
authors.forename: Takumi
authors.initials: T
authors.lastname: Misaka
authors.forename: Keiko
authors.initials: K
authors.lastname: Abe
mesh_terms: D001236:Aspergillus oryzae / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006023:Glycoproteins / Q000008:administration & dosage / Q000096:biosynthesis* / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015202:Protein Engineering / Q000379:methods; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000096:biosynthesis; D013549:Sweetening Agents / Q000008:administration & dosage / Q000737:chemistry* / Q000378:metabolism*; D013649:Taste / Q000187:drug effects
chemical_list: D006023:Glycoproteins; D011994:Recombinant Proteins; D013549:Sweetening Agents; C008533:miraculin protein, Synsepalum dulcificum