Monellin
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223553482
2008-07-04T16:12:58Z
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{{protein
| Name = '''Monellin chain A'''
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| HGNCid =
| Symbol = MONA_DIOCU
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| UniProt = P02881
| PDB = 1MOL
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{{protein
| Name = '''Monellin chain B'''
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| HGNCid =
| Symbol = MONB_DIOCU
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| EntrezGene =
| OMIM =
| RefSeq =
| UniProt = P02882
| PDB = 1MOL
| ECnumber =
| Chromosome =
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}}
'''Monellin''' is a sweet [[protein]] which was discovered in 1969 in the fruit of the West African shrub known as [[serendipity berry]] (''[[Dioscoreophyllum cumminsii]]''), it was first reported as a [[carbohydrate]].<ref name="jfs-34-408">GE Inglett, JF May. Serendipity berries - Source of a new intense sweetener. J Food Sci 1969, 34:408-411.</ref> The protein was named in 1972 after the [[Monell Chemical Senses Center]] in [[Philadelphia]], U.S.A., where the it was isolated and characterized.<ref name="jbc-248-534">[http://www.jbc.org/cgi/content/abstract/248/2/534 Characterization of Monellin, a Protein That Tastes Sweet. JA Morris, R Martenson, G Deibler and RH Cagan. J. Biol. Chem. 248 (2):534.]</ref>
== Protein composition ==
So far, five high intensity sweet proteins have been reported: monellin (1969), [[thaumatin]] (1972), [[pentadin]] (1989), [[mabinlin]] (1983) and [[brazzein]] (1994).<ref name=”2004-biopolymers”>[http://www.wiley-vch.de/books/biopoly/pdf_v08/vol08_08.pdf Biopolymers. Volume 8. Polyamides and Complex Proteinaceous Materials II. Sweet-tasting Proteins. I Faus and H Sisniega. p203-209. 2004. Eds. Wiley-VCH. ISBN 3-527-30223-9.]</ref> <br />
Monellin's molecular weight is 10.7 [[Atomic mass unit|kDa]]. Monellin is a two noncovalently associated polypeptide chains: an A chain sequence with 44 amino acid residues, and a B chain with 50 residues.<ref name="jbc-248-534">[http://www.jbc.org/cgi/content/abstract/248/2/534 Characterization of Monellin, a Protein That Tastes Sweet. JA Morris, R Martenson, G Deibler and RH Cagan. J. Biol. Chem. 248 (2):534.]</ref><ref>[http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=3614382 C Ogata, M Hatada, G Tomlinson, WC Shin and SH Kim. Crystal structure of the intensely sweet protein monellin. Nature. 1987 Aug 20-26;328(6132):739-42.]</ref>
<blockquote>
Monellin chain A (44 AA): <br />
<tt>REIKGYEYQL YVYASDKLFR ADISEDYKTR GRKLLRFNGP VPPP</tt><br />
Monellin chain B (50 AA): <br />
<tt>GEWEIIDIGP FTQNLGKFAV DEENKIGQYG RLTFNKVIRP CMKKTIYEEN</tt><br />
''[[Amino acid#Table of standard amino acid abbreviations and side chain properties |Amino acid]] sequence of the sweet protein monellin adapted from Swiss-Prot biological database of protein.<ref>[http://www.expasy.org/uniprot/P02881 UniProtKB/Swiss-Prot database entry #P02881]</ref><ref>[http://www.expasy.org/uniprot/P02882 UniProtKB/Swiss-Prot database entry #P02882]</ref>''</blockquote>
===MNEI===
The A and B chains of monellin are linked with a Gly-Phe di[[peptide bond]] into the single chain sweet protein MNEI, an artificial engineered protein.<ref name="MNEI">{{cite journal | author = Spadaccini R, Crescenzi O, Tancredi T, De Casamassimi N, Saviano G, Scognamiglio R, Di Donato A, Temussi PA | title = Solution structure of a sweet protein: NMR study of MNEI, a single chain monellin | journal = Journal of Molecular Biology | volume = 305 | issue = 3 | pages = 505–14 | date = 19 January 2001 | url = http://www.ncbi.nlm.nih.gov/Structure/mmdb/mmdbsrv.cgi?Dopt=s&uid=14589 | pmid = 11152608 | accessdate = 18 May 2008 | doi = 10.1006/jmbi.2000.4304}}</ref>
== Sweetness properties ==
The relative sweetness of monellin varies from 800 to 2000 times sweeter than sucrose, depending on the sweet reference it is assessed against. It is reported to be 1500-2000 times sweeter than a 7% sucrose solution on a weight basis<ref name="APR-25-725”>[http://www.rti.org/abstract.cfm?pid=2062 Kim NC, Kinghorn AD (2002) Highly sweet compounds of plant origin. Archives of Pharmacal Research 25, 725-746.]</ref><ref name="Kinghorn-book2">AD kinghorn and CM Compadre. Less common high-potency sweeteners. In Alernative Sweeteners: Second Edition, Revised and Expanded, L O'Brien Nabors,Ed., New York, 1991. ISBN 0-8247-8475-8.</ref> and 800 times sweeter than sucrose when compared with a 5% sucrose solution on a weight basis.<ref name=”patent-702199”>[http://www.freepatentsonline.com/4122205.html Burge, M.L.E. and Nechutny, Z. Sweetening compositions containing protein sweeteners. Tate & Lyle Ltd. 702199. 1978.]</ref>
Monellin has a slow onset of sweetness and lingering aftertaste. Like [[miraculin]], monellin's sweetness is pH dependent; the protein is tasteless below pH 2 and above pH 9.
Blending the sweet protein with bulk and/or intense sweeteners reduces the persistent sweetness and shows a synergistic sweet effect.<ref name="Kinghorn-book3">Kinghorn, A.D. and Compadre, C.M. Alernative Sweeteners: Third Edition, Revised and Expanded, Marcel Dekker ed., New York, 2001. ISBN 0-8247-0437-1</ref><br />
Heat over 50ºC at low pH denatures monellin proteins causing a loss of the sweetness.<ref name="Kinghorn-book3">Kinghorn, A.D. and Compadre, C.M. Alternative Sweeteners: Third Edition, Revised and Expanded, Marcel Dekker ed., New York, 2001. ISBN 0-8247-0437-1</ref>
==As a sweetener ==
Monellin can be useful for [[sweetener|sweetening]] some foods and drinks as it is a protein readily soluble in water. However it may have limited application because it denatures under high temperature conditions which makes it unsuitable for processed food. It may be relevant as tabletop sweetener.<br />
In addition, monellin is costly to extract from the fruit and the plant is difficult to grow. Alternative production such as chemical synthesis and expression in [[micro-organisms]] are being investigated. For instance, monellin has been expressed successfully in [[yeast]] (''[[Candida utilis]]'')<ref name=”joceoj-35-654”>XL Zhang, T Ito, K Kondo, T Kobayashi and H Honda. Production of single chain recombinant monellin by high cell density culture of genetically engineered Candida utilis using limited feeding of sodium ions. Journal of Chemical Engineering of Japan 2002. 35: 654-659.</ref> and synthesised by solid-phase method.<ref name=”paac-74-1235”>[http://www.iupac.org/publications/pac/2002/pdf/7407x1235.pdf M Kohmura, T Mizukoshi, N Nio, EI Suzuki and Y Ariyoshi. Structure–taste relationships of the sweet protein monellin. Pure Appl. Chem., Vol. 74, 1235-1242, 2002.]</ref> The synthetic monellin produce by yeast was found to be 4000 times sweeter than sucrose when compared to 0.6% sugar solution.<br />
Legal issues are the main barrier in widespread use as a sweetener as Monellin has no legal status in the [[European Union]] or the [[United States]]. However, it is approved in [[Japan]] as a harmless [[additive]], according to the List of Existing Food Additives issued by the Ministry of Health and Welfare (published in English by [[JETRO]]).
== See also ==
*[[Curculin]]
*[[Thaumatin]]
*[[Miraculin]]
*[[Stevia]]
== References ==
{{Reflist}}
[[Category:Sweeteners]]
[[Category:Proteins]]
{{protein-stub}}
[[de:Monellin]]