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Title:   Author  item
                                            Friedman, Mendelitem
                                            Brandon, David
  Submitted to: Meeting Abstract
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 10/15/1999
                                    Publication  Date: 3/1/2000
                                    Citation: Friedman, M., Brandon, D.L. 2000. Nutritional improvement of soy proteins through disulfide interchange. [Abstract]. 219th American Chemical Society National Meeting, 26-30 March 2000, San Francisco, CA. Abstract No. AGFD-158.Interpretive Summary:
                                Technical Abstract: Treatment of raw soy flour with L-cysteine,  N-acetyl-L-cysteine, reduced glutathione or sodium sulfite results in the introduction of  new half-cyst esidues into sulfur-poor legume proteins and the formation of mixed disulfide bonds among the added SH-compounds, Bowman-Birk and Kunitz protease inhibitors, and other seed storage proteins.  These  modifications lead to loss of inhibitory activity measured by both enzyme assays  and ELISAs  (immunoassays specific for the active forms of both inhibitors) and increased protein digestibility and nutritive value.  On a molar basis, sodium sulfite was the most effective in facilitating inactivation of trypsin inhibitors in soy flour.  The mechanism of inactivation is postulated to be due to the interchange and/or reduction of protein disulfide bonds to form rearranged proteins with decreased ability to complex with trypsin or chymotrypsin.  This proposed mechanism  is supported by the  observation that N-acetyl-L-cysteine inactivated lima bean lectin, a disulfide-containing protein, but failed to inactivate soybean lectin which lacks disulfide bonds. The results suggest that controlled disulfide exchange may be useful for the inactivation of other disulfide-containing toxic proteins, including ricin, bacterial toxins, and food allergens.


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