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, respon ...
s extracted from the seed of
mabinlang (''
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 sequences
In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is called ...
(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
UniProt is a freely accessible database of protein sequence and functional information, many entries being derived from genome sequencing projects. It contains a large amount of information about the biological function of proteins derived fro ...
biological database of protein.
The molecular weights of Mabinlin-1, Mabinlin-3 and Mabinlin-4 are 12.3
kDa
The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at re ...
, 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 ...
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 temperature ...
,
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 refi ...
on molar basis, 10 times sucrose on a weight basis,
which make them less sweet than
thaumatin
Thaumatin (also known as talin) is a low-calorie sweetener and flavor modifier. The protein is often used primarily for its flavor-modifying properties and not exclusively as a sweetener.
The thaumatins were first found as a mixture of prote ...
(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
{{Wiktionary, sweetener
A sweetener is a substance added to food or drink to impart the flavor of sweetness, either because it contains a type of sugar, or because it contains a sweet-tasting sugar substitute. Many artificial sweeteners have be ...
.
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 Un ...
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
Brazzein is a sweet-tasting protein extracted from the West African fruit of the climbing plant Oubli (''Pentadiplandra brazzeana'' Baillon). It was first isolated by the University of Wisconsin–Madison in 1994.
Brazzein is found in the extra ...
*
Monellin
Monellin, a sweet protein, 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.GE Inglett, JF May. Serendipity berries - Source of a ...
*
Pentadin
*
Thaumatin
Thaumatin (also known as talin) is a low-calorie sweetener and flavor modifier. The protein is often used primarily for its flavor-modifying properties and not exclusively as a sweetener.
The thaumatins were first found as a mixture of prote ...
References
External links
*{{Commonscatinline
Sugar substitutes
Proteins