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Abstract

Fibrinolytic enzyme nattokinase was first extracted from a traditional Japanese fermented soybean food, Natto. Edible red alga Porphyra dentata shares similar high protein content with soybean. In this study, we successfully purify and characterize nattokinase from the cultural filtrate of P. dentata fermented by Bacillus subtilis N1. The crude enzyme was purified by ion-exchange and gel filtration to reach electrophoretic homogeneity. The nattokinase, which has a molecular weight of 46.5 kDa and an isoelectric point of 8.35, was stable from pH 5 to 9 and at temperatures up to 55°C, and it showed optimum enzyme activity at pH 8 and at 55°C. This enzyme is characterized as a serine-protease, and its activity can be stimulated by adding CuSO4 or FeCl3. Our results identified the fibrinolytic nattokinase in the cultural filtrate of P. dentata fermented by Bacillus subtilis N1 and provided affecting factors to its fibrinolytic activity.

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