Mabinlins are
sweet-tasting protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
s extracted from the seed of
mabinlang
''Capparis masaikai'', known as mabinlang,Data Portal of the Global Biodiversity Information Facility (GBIF)Biodiversity occurrence data for Capparis masaikai H. Léveillé grows in the subtropical region of the Yunnan province of China and bear ...
(''
Capparis masaikai Levl.''), a plant growing in
Yunnan
Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the ...
province of China. There are four homologues. Mabinlin-2 was first isolated in 1983
and characterised in 1993,
and is the most extensively studied of the four. The other variants of mabinlin-1, -3 and -4 were discovered and characterised in 1994.
Protein structures
The 4 mabinlins are very similar in their
amino acids
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...
sequences (see below).
''Chain A''
M-1:
M-2:
M-3:
M-4:
''Chain B''
M-1:
M-2:
M-3:
M-4:
''Amino acid sequence of Mabinlins homologues are adapted from Swiss-Prot biological database of protein.
The molecular weights of Mabinlin-1, Mabinlin-3 and Mabinlin-4 are 12.3
kDa, 12.3 kDa and 11.9 kDa, respectively.
With a molecular weight of 10.4kDa, mabinlin-2 is lighter than mabinlin-1. It is a heterodimer consisting of two different chains A and B produced by post-translational cleavage. The A chain is composed of 33 amino acid residues and the B chain is composed of 72 amino acid residues. The B chain contains two intramolecular
disulfide bond
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...
s and is connected to the A chain through two intermolecular disulfide bridges.
Mabinlin-2 is the sweet-tasting protein with the highest known
thermostability
In materials science and molecular biology, thermostability is the ability of a substance to resist irreversible change in its chemical or physical structure, often by resisting decomposition or polymerization, at a high relative temperatu ...
,
which is due to the presence of the four disulfide bridges.
It has been suggested also that the difference in the heat stability of the different mabinlin homologues is due to the presence of an arginine residue (heat-stable homologue) or a glutamine (heat-unstable homologue) at position 47 in the B-chain.
The sequences of Mabilins cluster with Napins ().
Sweetness properties
Mabinlins sweetness were estimated to be about 100-400 times that of
sucrose
Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula .
For human consumption, sucrose is extracted and refine ...
on molar basis, 10 times sucrose on a weight basis,
which make them less sweet than
thaumatin (3000 times) but elicit a similar sweetness profile.
The sweetness of mabinlin-2 is unchanged after 48 hours incubation at 80 °C.
Mabinlin-3 and -4 sweetness stayed unchanged after 1 hour at 80 °C, while mabinlin-1 loses sweetness after 1 hour at the same condition.
As a sweetener
Mabinlins, as proteins, are readily soluble in water and found to be highly sweet; however, mabinlin-2 with its high heat stability has the best chance to be used as a
sweetener.
During the past decade, attempts have been made to produce mabinlin-2 industrially. The sweet-tasting protein has been successfully synthesised by a stepwise solid-phase method in 1998, however the synthetic protein had an astringent-sweet taste.
Mabinlin-2 has been expressed in
transgenic
A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...
potato
The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae.
Wild potato species can be found from the southern Uni ...
tubers, but no explicit results have been reported yet.
However, patents to protect production of recombinant mabinlin by cloning and DNA sequencing have been issued.
See also
*
Brazzein
*
Monellin
*
Pentadin
Pentadin, a sweet-tasting protein, was discovered and isolated in 1989, in the fruit of Oubli ('' Pentadiplandra brazzeana'' ), a climbing shrub growing in some tropical countries of Africa.
The fruit has been consumed by the apes and the native ...
*
Thaumatin
References
External links
*{{Commonscatinline
Sugar substitutes
Proteins