Also known as: Mabinlin II, MAB II
Mabinlins are sweet-tasting proteins 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.
M-1: EPLCRRQFQQ HQHLRACQRY IRRRAQRGGL VD
M-2: QLWRCQRQFL QHQRLRACQR FIHRRAQFGG QPD
M-3: EPLCRRQFQQ HQHLRACQRY LRRRAQRGGL AD
M-4: EPLCRRQFQQ HQHLRACQRY LRRRAQRG
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.
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 bonds 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.
Mabinlins sweetness were estimated to be about 100-400 times that of sucrose 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.
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 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.
- Hu Z, He M (1983). "Studies on mabinlin, a sweet protein from the seeds of Capparis masaikai levl. I. extraction, purification and certain characteristics". Acta Botan. Yunnan. (5): 207–212.
- Liu X, Maeda S, Hu Z, Aiuchi T, Nakaya K, Kurihara Y (January 1993). "Purification, complete amino acid sequence and structural characterization of the heat-stable sweet protein, mabinlin II". European Journal of Biochemistry. 211 (1–2): 281–7. doi:10.1111/j.1432-1033.1993.tb19896.x. PMID 8425538.
- Nirasawa S, Nishino T, Katahira M, Uesugi S, Hu Z, Kurihara Y (August 1994). "Structures of heat-stable and unstable homologues of the sweet protein mabinlin. The difference in the heat stability is due to replacement of a single amino acid residue". European Journal of Biochemistry. 223 (3): 989–95. doi:10.1111/j.1432-1033.1994.tb19077.x. PMID 8055976.
- Kohmura M, Ariyoshi Y (October 1998). "Chemical synthesis and characterization of the sweet protein mabinlin II". Biopolymers. 46 (4): 215–23. doi:10.1002/(SICI)1097-0282(19981005)46:4<215::AID-BIP3>3.0.CO;2-S. PMID 9715665.
- Guan RJ, Zheng JM, Hu Z, Wang DC (July 2000). "Crystallization and preliminary X-ray analysis of the thermostable sweet protein mabinlin II". Acta Crystallographica Section D. 56 (Pt 7): 918–9. doi:10.1107/S0907444900005850. PMID 10930844.
- Nirasawa S, Liu X, Nishino T, Kurihara Y (October 1993). "Disulfide bridge structure of the heat-stable sweet protein mabinlin II". Biochimica et Biophysica Acta. 1202 (2): 277–80. doi:10.1016/0167-4838(93)90016-K. PMID 8399391.
- Kurihara Y (1992). "Characteristics of antisweet substances, sweet proteins, and sweetness-inducing proteins". Critical Reviews in Food Science and Nutrition. 32 (3): 231–52. doi:10.1080/10408399209527598. PMID 1418601.
- Kurihara Y, Nirasawa S (1997). "Structures and activities of sweetness-inducing substances (miraculin, curculin, strogin) and the heat-stable sweet protein, mabinlin" (PDF). Foods and Food Ingredients Journal of Japan (174): 67–74.
- Xiong LW, Sun S (1996). "Molecular cloning and transgenic expression of the sweet protein mabinlin in potato tubers". Plant Physiology. 111 (2): 147.
- US granted 6051758, Sun S, Xiong L, Hu Z, Chen H, "Recombinant Sweet protein Mabinlin", issued 18 April 2000, assigned to University of Hawaii
- Media related to Mabinlin at Wikimedia Commons