Degradation Sequence of Glycinin by Tryptic Hydrolysis

Native glycinin was split by trypsin in limited regions under high ionic strength condition and converted into glycinin-T. Initially, the intermediary subunits of glycinin converted into fragments of 48,000 (IST-T) and 44,500 (IST-2) molecular weights. These fragments were transitory intermediates and then they were cleaved yielding fragments of 32,500 (IST-3) and 29,000 (IST-4) molecular weights. Analyses of the mole fractions of the fragments revealed that IST-2 was rapidly split into IST-4 followed by splitting of IST-1 into IST-3.

Subsequently, glycinin-T was dissociated with 6 m urea and subjected to gel filtration and ion exchange chromatography in order to isolate IST-3 and IST-4. Acidic-urea gel electrophoresis of the isolated 1ST showed that IST-3 contained B₁ B₂ and B₃ subunits, whereas IST-4 contained B₄ subunit. These results indicated that IST-3 was formed from IS—1 and IS-2, and IST-4 from IS-3.