title: Riboflavin-binding protein exhibits selective sweet suppression toward protein sweeteners.
abstract: Riboflavin-binding protein (RBP) is well known as a riboflavin carrier protein in chicken egg and serum. A novel function of RBP was found as a sweet-suppressing protein. RBP, purified from hen egg white, suppressed the sweetness of protein sweeteners such as thaumatin, monellin, and lysozyme, whereas it did not suppress the sweetness of low molecular weight sweeteners such as sucrose, glycine, D-phenylalanine, saccharin, cyclamate, aspartame, and stevioside. Therefore, the sweet-suppressing activity of RBP was apparently selective to protein sweeteners. The sweet suppression by RBP was independent of binding of riboflavin with its molecule. Yolk RBP, with minor structural differences compared with egg white RBP, also elicited a weaker sweet suppression. However, other commercially available proteins including ovalbumin, ovomucoid, beta-lactogloblin, myoglobin, and albumin did not substantially alter the sweetness of protein sweeteners. Because a prerinse with RBP reduced the subsequent sweetness of protein sweeteners, whereas the enzymatic activity of lysozyme and the elution profile of lysozyme on gel permeation chromatography were not affected by RBP, it is suggested that the sweet suppression is caused by an interaction of RBP with a sweet taste receptor rather than with the protein sweeteners themselves. The selectivity in the sweet suppression by RBP is consistent with the existence of multiple interaction sites within a single sweet taste receptor.
authors.affiliation: Department of Fermentation Science, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Tokyo 156-8502, Japan. maehashi@nodai.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Maehashi
authors.forename: Mami
authors.initials: M
authors.lastname: Matano
authors.forename: Azusa
authors.initials: A
authors.lastname: Kondo
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Shigezo
authors.initials: S
authors.lastname: Udaka
mesh_terms: D000818:Animals; D002645:Chickens; D004527:Egg Proteins / Q000302:isolation & purification / Q000494:pharmacology; D026901:Membrane Transport Proteins / Q000302:isolation & purification / Q000494:pharmacology*; D008970:Molecular Weight; D011956:Receptors, Cell Surface / Q000502:physiology; D013549:Sweetening Agents / Q000494:pharmacology*; D013649:Taste / Q000187:drug effects; D013652:Taste Threshold / Q000187:drug effects*
chemical_list: D004527:Egg Proteins; D026901:Membrane Transport Proteins; D011956:Receptors, Cell Surface; D013549:Sweetening Agents; C019079:riboflavin-binding protein