LIMITED TRYPTIC DEGRADATION OF UREA DENATURED GLYCININ

Digestibilities of native, 5 M urea-denatured and 8 M urea-denatured glycinin were studied. Urea was removed by dialysis before digestion. The tryptic digestion of the proteins are influenced by ionic strength. Under low ionic strength condition (0 M NaCl), the proteins, even native glycinin, are well degraded. On the other hand, under high ionic strength condition (0.5 M NaCl), native glycinin resists the tryptic attack and 5 M urea-denatured glycinin is best degraded. The digestibility of 8 M urea-denatured glycinin is lower than that of 5 M urea-denatured one under the condition. The gel filtration and electrophoretic properties show that the digestion intermediate like glycinin-T (the intermediate from native glycinin) is contained in the digestion products. These suggest that the urea-denatured protein contains the almost renatured component after removal of urea. A larger amount of the glycinin-Tlike protein was detected at 8 M urea denaturation than at 5 M urea. Therefore, glycinin renatures more readily from 8 M urea denaturation. Probably this is the cause of the decreased digestibility at 8 M urea denaturation. © 1979 Taylor & Francis Group, LLC.