ネムノキ(Albizia julibrissin)種子中の凝乳 : プロテアーゼの精製とその性質

概要

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Gouda type cheese was prepared with a milk clotting enzyme partially purified from the young seeds of Albizia julibrissin. The yield of green cheese made with the enzyme was comparable to that made with chymosin. In terms of flavor, the enzyme did not develop any bitterness in the cheese after 3 months of ripening. Hence, the milk clotting enzyme was purified about 20-fold and we examined some properties.The purified enzyme showed a single band via sodium dodecyl-sulfate-polyacryl- amide gel electrophoresis (SDS-PAGE). The molecular weight estimated by both gel filtration and SDS-PAGE was 21, 000 and 28, 000, respectively. The optimum pH for proteolytic activity of the enzyme was around 6.0, while the optimum temperature was at 65°. The enzyme was most stable around pH 6.0. Proteolytic activity was lost at temperatures higher than 50°, and about 50% of the original activity was lost after incubation at 60° for 30min.On the other hand, proteolytic activity was inhibited by p-chloromercuribenzoic acid, N-ethylmaleimide, antipain and leupeptin, and was activated by dithiothreitol and L-cysteine. This indicates that the purified enzyme belongs to papain-like cysteine protease.