Mabinlin
Encyclopedia
Mabinlins are sweet-tasting protein
s extracted from the seed of Mabinlang (Capparis masaikai
Levl.), a Chinese plant growing in Yunnan
province. 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.
(see below).
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. 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
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
, 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.
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.
.
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
potato
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.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s extracted from the seed of Mabinlang (Capparis masaikai
Capparis masaikai
Capparis masaikai, known as Mabinlang, grow in the subtropical region of the Yunnan province ofChina and bear fruits of tennis-ball size. The matured seed are used in traditional Chinese medicine....
Levl.), a Chinese plant growing in Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...
province. 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 sequencesPeptide sequence
Peptide sequence or amino acid sequence is the order in which amino acid residues, connected by peptide bonds, lie in the chain in peptides and proteins. The sequence is generally reported from the N-terminal end containing free amino group to the C-terminal end containing free carboxyl group...
(see below).
Chain A
M-1: EPLCRRQFQQ HQHLRACQRY IRRRAQRGGL VD
M-2: QLWRCQRQFL QHQRLRACQR FIHRRAQFGG QPD
M-3: EPLCRRQFQQ HQHLRACQRY LRRRAQRGGL AD
M-4: EPLCRRQFQQ HQHLRACQRY LRRRAQRG
Chain B
M-1: EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRQLFR AARNLPNICK IPAVGRCQFT RW
M-2: QPRRPALRQC CNQLRQVDRP CVCPVLRQAA QQVLQRQIIQ GPQQLRRLFD AARNLPNICN IPNIGACPFR AW
M-3: EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRRLFR AARNLPNICK IPAVGRCQFT RW
M-4: EQRGPALRLC CNQLRQVNKP CVCPVLRQAA HQQLYQGQIE GPRQVRRLFR AARNLPNICK IPAVGRCQFT RW
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
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
, 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. 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
Disulfide bond
In chemistry, a disulfide bond is a covalent bond, usually derived by the coupling of two thiol groups. The linkage is also called an SS-bond or disulfide bridge. The overall connectivity is therefore R-S-S-R. The terminology is widely used in biochemistry...
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
Thermostability
Thermostability is the quality of a substance to resist irreversible change in its chemical or physical structure at a high relative temperature.Thermostable materials may be used industrially as fire retardants...
, 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.
Sweetness properties
Mabinlins sweetness were estimated to be about 100-400 times that of sucroseSucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...
on molar basis, 10 times sucrose on a weight basis, which make them less sweet than thaumatin
Thaumatin
Thaumatin is a low-calorie sweetener and flavour modifier. The substance, a natural protein, is often used primarily for its flavour-modifying properties and not exclusively as a sweetener....
(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 sweetenerSugar substitute
A sugar substitute is a food additive that duplicates the effect of sugar in taste, usually with less food energy. Some sugar substitutes are natural and some are synthetic. Those that are not natural are, in general, called artificial sweeteners....
.
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
Genetically modified organism
A genetically modified organism or genetically engineered organism is an organism whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one...
potato
Potato
The potato is a starchy, tuberous crop from the perennial Solanum tuberosum of the Solanaceae family . The word potato may refer to the plant itself as well as the edible tuber. In the region of the Andes, there are some other closely related cultivated potato species...
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.