Document Detail

The sulfhydryl group of monellin: its chemical reactivity and importance to the sweet taste.
MedLine Citation:
PMID:  967895     Owner:  NLM     Status:  MEDLINE    
The presence of a single cysteine in the sweet-tasting protein monellin was confirmed by titrations with p-hydroxymercuribenzoate (PHMB) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). The sulfhydryl group in native monellin reacts very slowly with each of these reagents, indicating that the sulfhydryl is relatively inaccessible. In the presence of either 6 M guanidine-HCl, 8 M urea, or 1% sodium dodecyl sulfate, the rate of reaction of the sulfhydryl group with titrant is dramatically increased. Under a variety of conditions, the presence of 1 mole of sulfhydryl per mole of protein (of molecular weight 10,700) was found. Reaction of the sulfhydryl by titration with PHMB or DTNB leads to loss of sweetness. The free sulfhydryl is also lost by carboxymethylation of monellin in the presence of guanidine-HCl, yielding a protein that is not sweet. Exposure to air in the presence of denaturant leads to a decrease in the sweetness of monellin. Sweetness of the PHMB-reacted monellin can be recovered upon treatment of the protein with mercaptoethanol, and the partial loss of sweetness that occurs with air exposure is lessened in the presence of mercaptoethanol. It is postulated that alteration of the single sulfhydryl group of monellin leads to a change in the tertiary structure of the protein and hence its sweet taste.
R H Cagan; J A Morris
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)     Volume:  152     ISSN:  0037-9727     ISO Abbreviation:  Proc. Soc. Exp. Biol. Med.     Publication Date:  1976 Sep 
Date Detail:
Created Date:  1976-11-21     Completed Date:  1976-11-21     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  7505892     Medline TA:  Proc Soc Exp Biol Med     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  635-40     Citation Subset:  IM    
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MeSH Terms
Chemical Phenomena
Dithionitrobenzoic Acid
Plant Proteins* / metabolism
Protein Denaturation
Structure-Activity Relationship
Sulfhydryl Compounds*
Sweetening Agents*
Taste / physiology*
Reg. No./Substance:
0/Hydroxymercuribenzoates; 0/Plant Proteins; 0/Sulfhydryl Compounds; 0/Sweetening Agents; 52-90-4/Cysteine; 69-78-3/Dithionitrobenzoic Acid

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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