水産動物のキチン分解酵素に関する研究-V : ハマチの消化管に存在するキチン分解酵素について

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In the previous paper1) it was reported by the present authors that the chitinolytic enzyme is present in some organs of a few kinds of aquatic animals. Recently, it has been reported that in the digestive tracts of Japanese sea-bass, Latsolabrax japonicus, chitin seems to be decomposed simultaneously by both bacterial and non-bacterial actions.2) The present study was carried out in order to ascertain whether similar chitinolytic systems are present in yellow tail, Seriola quinqueradiata. This paper is concerned with both chitinolytic enzyme of non-bacterial origin in the stomach and chitin-decomposing bacteria present in the digestive tracts. Results obtained were as follows: 1) The chitinolytic enzyme of high activity is present in the stomach but not in the pyloric caeca and intestine at all (Table 1). 2) The optimum pH value for the action of the enzyme is about 4.0 (Fig. 2), and the optimum temperature is about 50°C (Fig. 3). 3) The enzyme is stable at pH 3.0-4.0 at 22°C at least for 24 hours (Fig. 4). 4) Most or many of the bacterial cells present in the digestive tracts are occupied by chitin-decomposing ones (Table 2). 5) The optimum pH values for the action of the enzyme of bacterial origin is about 7.0 (Fig. 5), and the optimum temperature is about 40°C (Fig. 6), both being in sharp contrast to those of the enzyme of non-bacterial origin.
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