title: Riboflavin-binding protein is a novel bitter inhibitor.
abstract: Riboflavin-binding protein (RBP) from chicken egg, which was recently reported to be a selective sweet inhibitor for protein sweeteners, was also found to be a bitter inhibitor. RBP elicited broadly tuned inhibition of various bitter substances including quinine-HCl, naringin, theobromine, caffeine, glycyl-L-phenylalanine (Gly-Phe), and denatonium benzoate, whereas several other proteins, such as ovalbumin (OVA) and beta-lactoglobulin, were ineffective in reducing bitterness of these same compounds. Both the bitter tastes of quinine and caffeine were reduced following an oral prerinse with RBP. It was found that RBP binds to quinine but not to caffeine, theobromine, naringin, and Gly-Phe. However, the binding of RBP to quinine was probably not responsible for the bitter inhibition because OVA bound to quinine as well as RBP. Based on these results, it is suggested that the bitter inhibitory effect of RBP is the consequence of its ability to interact with taste receptors rather than because it interacts with the bitter tastants themselves. RBP may have practical uses in reducing bitterness of foods and pharmaceuticals. It may also prove a useful tool in studies of mechanisms of bitter taste.
authors.affiliation: Department of Fermentation Science, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, 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: Miho
authors.initials: M
authors.lastname: Nonaka
authors.forename: Shigezo
authors.initials: S
authors.lastname: Udaka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D000135:Acid Phosphatase / Q000737:chemistry; D000328:Adult; D002110:Caffeine / Q000737:chemistry / Q000378:metabolism; D004151:Dipeptides / Q000737:chemistry / Q000378:metabolism; D004529:Egg White / Q000737:chemistry; D004530:Egg Yolk / Q000737:chemistry; D005260:Female; D044950:Flavanones / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007782:Lactoglobulins / Q000494:pharmacology; D008297:Male; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010047:Ovalbumin / Q000378:metabolism / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D011803:Quinine / Q000737:chemistry / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D013649:Taste / Q000187:drug effects*; D013805:Theobromine / Q000737:chemistry / Q000378:metabolism; D000098706:Taste Receptors, Type 2
chemical_list: D000135:Acid Phosphatase; D002110:Caffeine; D004151:Dipeptides; D044950:Flavanones; D007782:Lactoglobulins; D026901:Membrane Transport Proteins; D010047:Ovalbumin; D000644:Quaternary Ammonium Compounds; D011803:Quinine; D043562:Receptors, G-Protein-Coupled; D012710:Serum Albumin, Bovine; D013805:Theobromine; D000098706:Taste Receptors, Type 2; C019079:riboflavin-binding protein; C029660:glycylphenylalanine; C005274:naringin; C043414:denatonium