Glycinin subunits

Thermal aggregation of glycinin subunits. Cereal Chem.,... 

Cho et al. (1989) studied the inheritance of the glycinin subunits of soybean seed storage protein. They identified five genes, one of which had a third allele. Palmer et al. (2004) discuss these loci and loci associated with protease inhibitors and peroxidase. 

Table 8.1. Sulfur Amino Acid Content of Glycinin Subunits (modified from Staswick et al., 1981 and Utsumi et al., 1997)...

Barton, K.A., Thompson, J.F., Madison, J.T., Rosenthal, R., Jarvis, N.P., and Beachy, R.N. The biosynthesis and processing of high molecular weight precursors of soybean glycinin subunits. Biol. Chem. 257(11) 6089-6095, June 1982. 

P. E. Staswick, M. A. Hermodson, and N. C. Nielsen, Identification of the cystines which fink the acidic and basic components of the glycinin subunits, J. Biol. Chem. 259, 13431-13435 (1984). 

Arachin, the counterpart of glycinin in peanuts, consists of subunits of 60,000—70,000 mol wt which on reduction with 2-mercaptoethanol yield polypeptides of 41,000—48,000 and 21,000 mol wt (17) analogous to the behavior of glycinin. In addition to the storage proteins, oilseeds contain a variety of minor proteins, including trypsin inhibitors, hemagglutinins, and enzymes. Examples of the last are urease and Hpoxygenase in soybeans. 

The formation of reversible aggregates has previously been observed by Catsimpoolas tt aZ., (7) with the glycinin or the 11S fraction. They suggested that the reversible aggregation was due to intermolecular interactions of undissociated molecules and that aggregates formed at temperatures above 70UC originated from dissociated subunits. 

Choi, S.K. M. Adachi S. Utsumi. Identification of the bile acid-binding region in the soy glycinin AlaBlb subunit. Biosci. Biotechnol. Biochem 2002, 66, 2395—2401. 

Itoh, T. M. Adachi T. Masuda B. Mikami S. Utsumi. Crystal strucmre of recombinant soybean proglycinin subunit, its comparison with mature glycinin A B subunit, responsible for hex-amer assembly. Deposited 2005. http //www.rcsb.org/pdb/explore.do structureld=2D5F. 

Krishnan, H.B. S.S. Natarajan A.A. Mahmoud R. Nelson. Identification of glycinin and P-conglycinin subunits that contribute to the increased protein content of high-protein soybean lines./. Agric. Food Chem. 2007, 55, 1839-1845. 

Tezuka, M. H. Taira Y. Igarashi K. Yagasaki T. Ono. Properties of tofus and soymilks prepared from soybeans having different subunits of glycinin. J. Agric. Food Chem. 2000, 48, 111 1—1117. 

Glycinin and p-conglycinin have several subunits that can be dissociated by salt solution. Murray et al. (1980) patented a process that employs salt for extracting SPI at ionic strengths of 0.3 to 0.6 M, pH 5.0 to 6.8 and 15 to 25°C (60 to 78°F). The extract is then concentrated to one-fourth to one-third its volume and diluted to an ionic strength of <0.2 M to form protein micelles that precipitate into an amorphous mass and are dried or further processed. 

The adsorption of soy protein at an interface is relatively slow compared to casein, and the rate is affected by ionic strength, being higher at 0.2 M than at zero NaCl where the subunits may be dissociated. Conceivably the reduction of the zeta potential and electrostatic repulsion (from 0 to 0.2 M salt) facilitates penetration and subsequent surface packing (28). The rate of penetration of additional molecules into the film indicated that the soy proteins initially adsorbed and spread easily at the surface ( ). However, this seems inconsistent with the highly stable disulfide linked tertiary structure of soy glycinin (30) and it is perhaps the conglycinin component that forms the initial interfacial film (31). 

Glycinin chief protein component of soybeans. It is stored in subcellular particles, known as protein bodies . The dimer (Af, 350,000) consists of 12 subunits (M, 28,500 each) 6 of these chains are acidic (pi 3.0-3.4) and 6 are basic (pi 8.0-8.5). G is structurally related to the protein Arachin (see). 

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