Monellin

From Wikipedia, the free encyclopedia

'Monellin chain A'
Identifiers
Symbol MONA_DIOCU
PDB 1MOL
UniProt P02881
Other data
'Monellin chain B'
Identifiers
Symbol MONB_DIOCU
PDB 1MOL
UniProt P02882
Other data

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.[1] The protein was named in 1972 after the Monell Chemical Senses Center in Philadelphia, U.S.A., where the it was isolated and characterized.[2]

Contents

[edit] Protein composition

So far, five high intensity sweet proteins have been reported: monellin (1969), thaumatin (1972), pentadin (1989), mabinlin (1983) and brazzein (1994).[3]
Monellin's molecular weight is 10.7 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.[2][4]

Monellin chain A (44 AA):
REIKGYEYQL YVYASDKLFR ADISEDYKTR GRKLLRFNGP VPPP
Monellin chain B (50 AA):
GEWEIIDIGP FTQNLGKFAV DEENKIGQYG RLTFNKVIRP CMKKTIYEEN
Amino acid sequence of the sweet protein monellin adapted from Swiss-Prot biological database of protein.[5][6]

[edit] MNEI

The A and B chains of monellin are linked with a Gly-Phe dipeptide bond into the single chain sweet protein MNEI, an artificial engineered protein.[7]


[edit] 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[8][9] and 800 times sweeter than sucrose when compared with a 5% sucrose solution on a weight basis.[10]

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.[11]
Heat over 50ºC at low pH denatures monellin proteins causing a loss of the sweetness.[11]

[edit] As a sweetener

Monellin can be useful for 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.
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)[12] and synthesised by solid-phase method.[13] The synthetic monellin produce by yeast was found to be 4000 times sweeter than sucrose when compared to 0.6% sugar solution.
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).

[edit] See also

[edit] References

  1. ^ GE Inglett, JF May. Serendipity berries - Source of a new intense sweetener. J Food Sci 1969, 34:408-411.
  2. ^ a b Characterization of Monellin, a Protein That Tastes Sweet. JA Morris, R Martenson, G Deibler and RH Cagan. J. Biol. Chem. 248 (2):534.
  3. ^ 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.
  4. ^ 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.
  5. ^ UniProtKB/Swiss-Prot database entry #P02881
  6. ^ UniProtKB/Swiss-Prot database entry #P02882
  7. ^ Spadaccini R, Crescenzi O, Tancredi T, De Casamassimi N, Saviano G, Scognamiglio R, Di Donato A, Temussi PA (19 January 2001). "Solution structure of a sweet protein: NMR study of MNEI, a single chain monellin.". Journal of Molecular Biology 305 (3): 505-14. PMID 11152608. 
  8. ^ Kim NC, Kinghorn AD (2002) Highly sweet compounds of plant origin. Archives of Pharmacal Research 25, 725-746.
  9. ^ 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.
  10. ^ Burge, M.L.E. and Nechutny, Z. Sweetening compositions containing protein sweeteners. Tate & Lyle Ltd. 702199. 1978.
  11. ^ a b 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
  12. ^ 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.
  13. ^ 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.
 This protein-related article is a stub. You can help Wikipedia by expanding it.
Languages