Characterization of proteins released from legume seeds in hot water.

When immersed in water at 50-60 degrees, mature soybean seeds release a large amount of protein. The major protein released was basic 7S globulin (Bg), which is present in the cotyledons of soybean seeds. The released Bg consisted of the 27,000 and 16,000 subunits which were linked by disulphide bonding and glycosylated. The released Bg exhibited an identical structure with the mature Bg which was synthesized in the normal developing seeds. Proteins like Bg were also found to be released into hot water from the seeds of legume species such as azuki-bean, cowpea, mung-bean and winged-bean. Besides Bg and Bg-like proteins, a few proteins including the 9,000 hydrophobic protein in soybean, ubiquitin in cowpea and mung-bean, and Kunitz trypsin inhibitor in winged-bean, were released from the seeds in hot water.