Abstract
In succession to the previous report on carbohydrases1), the proteolytic actions of the extracts from the digestive organs were investigated in various growth stages of rainbow trout. And the following results were obtained.
(1) The hydrolysis of casein by the extract from stomach was proceeded in acid side (optimal pH was 2.8), and that from pyloric caeca or intestine in alkaline side (optimal pH was 9.5).-(Fig. 1)
(2) The proteolytic activity of the extract form stomach was conspicuous in the early stages, and the stomach extract of the younger stage (body weight about 12g.) showed an almost same activity as that found in the middle stage (body weight about 100g.). In the later stage (body weight about 1, 000g.) the almost same activity was found.-(Table 2)
(3) On the other hand, the proteolytic activity of the extract from pyloric caeca and intestine was extremely low in the early stages (body weight less than about 4g.). It seemed that the activity increases with the growth of the fish, especially in the growth period from about 4 to 20g. of body weight. The highest activity was found in the extract of the middle stage, and after that the activity decreased gradually. The activity of the later stage was considerably low.-(Tables 1 and 2)
(4) The proteases of the digestive organs were active at relatively high temperatures (optimal temperatures were 40°-45°C), and lost markedly their activities at low temperatures.-(Fig. 2)
