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.
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.