Purification and Some Properties of N-Material in Soy Sauce

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N-Material was purified from soy sauce by dialysis against water and column chromatography on Sepharose 6B and DEAE-Sephadex A-50. The purified preparation was homogeneous on disc electrophoresis and the material consisted of almost pure protein with a trace amount of carbohydrate. The protein was characterized by higher contents of threonine, glycine, valine, isoleucine and lower contents of proline, cystaine and lysine than the soybean protein was. The molecular weight of the material was estimated to be approximately 210, 000 by Sephadex G-200 gel filtration method. N-Material, N-soy sauce and N-raw soy sauce gave a maximum turbidity at pH 5.0-5.5. N-Material gave four protein bands on SDS-polyacrylamide gel electrophoresis and their mobilities were 0.43, 0.51 (trace), 0.71 (major) and 1.05 (minor), whose molecular weights were 45, 000, 37, 000, 22, 500 and 11, 000, respectively. There was no clear protein band on polyacrylamide gel electrophoresis in the acidic-urea system. N-Material was digested by koji alkaline protease in low ionic strength, but not digested in the higher ionic condition.
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