Heat-induced formation of intermolecular disulfide linkages between thaumatin molecules that do not contain cysteine residues

Kaneko, R Kitabatake, N

R. Kaneko et N. Kitabatake, Heat-induced formation of intermolecular disulfide linkages between thaumatin molecules that do not contain cysteine residues, J AGR FOOD, 47(12), 1999, pp. 4950-4955

27

INGLESE

Article

Agricultural Chemistry","Chemistry & Analysis

JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

0021-8561 → ACNP

47

12

1999

4950 - 4955

ISI

0021-8561(199912)47:12<4950:HFOIDL>2.0.ZU;2-V

Thaumatin, a sweet protein that contains no cysteine residues and eight int ramolecular disulfide bonds, aggregates upon heating at pH 7.0 above 70 deg rees C, and its sweetness thereby disappears. The aggregate can be solubili zed by heating in the presence of both thiol reducing reagent and SDS. This molecular aggregation depended on the protein concentration during heating and was suppressed by the addition of N-ethylmaleimide or iodoacetamide, i ndicating a thiol-catalyzed disulfide interchange reaction between heat-den atured molecules. An amino acid analysis of the aggregates suggested that t he cysteine and lysine residues were reduced, and the formation of a cystei ne residue and a lysinoalanine residue was confirmed. The reduction and for mation of these residues stoichiometrically satisfied the beta-elimination of a cystine residue. The disulfide interchange reaction was catalyzed by c ysteine; that is, a free sulfhydryl residue was formed via beta-elimination of a disulfide bond. Intermolecular disulfide bonds were probably formed b etween thaumatin molecules upon heating at pH 7.0, which led to the aggrega tion of thaumatin molecules.