Structure-sweetness relationship in thaumatin: Importance of lysine residues

Citation
R. Kaneko et N. Kitabatake, Structure-sweetness relationship in thaumatin: Importance of lysine residues, CHEM SENSE, 26(2), 2001, pp. 167-177
Citations number
44
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Multidisciplinary,"Neurosciences & Behavoir
Journal title
CHEMICAL SENSES
ISSN journal
0379-864X → ACNP
Volume
26
Issue
2
Year of publication
2001
Pages
167 - 177
Database
ISI
SICI code
0379-864X(200102)26:2<167:SRITIO>2.0.ZU;2-#
Abstract
To clarify the structural basis for the sweetness of thaumatin I, lysine-mo dified derivatives and carboxyl-group-modified derivatives were prepared by chemical modification followed by chromatographic purification. The sweetn ess of derivatives was evaluated by sensory analysis. Phosphopyridoxylation of lysine residues Lys78, Lys97, Lys106, Lys137 and Lys187 markedly reduce d sweetness. The intensity of sweetness was returned to that of native thau matin by dephosphorylation of these phosphopyridoxylated lysine residues ex cept Lys106. Pyridoxamine modification of the carboxyl group of Asp21, Glu4 2, Asp60, Asp129 or Ala207 (C-terminal) did not markedly change sweetness. Analysis by far-UV circular dichroism spectroscopy indicated that the secon dary structure of all derivatives remained unchanged, suggesting that the l oss of sweetness was not a result of major disruption in protein structure. The five lysine residues, modification of which affected sweetness, are se parate and spread over a broad surface region on one side of the thaumatin I molecule. These lysine residues exist in thaumatin, but not in non-sweet thaumatin-like proteins, suggesting that these lysine residues are required for sweetness. These lysine residues may play an important role in sweetne ss through a multipoint interaction with a putative thaumatin receptor.