Über natürliche Aktivierung von Proteasen pflanzlicher Milchsäfte. Zwölfte Abhandlung über Pflanzenproteasen in der von R. Willstätter und Mitarbeitern begonnenen Untersuchungsreihe.

Abstract

Comparison of fresh papaya juice with commercial papain shows that the fresh juice varies in activity according to the degree of ripeness of the fruit. Similarly in the expressed juice of the pineapple, especially in the unripe fruit, the presence of an activator can be demonstrated which increases the effectiveness of the proteolytic enzyme to the same degree as that shown by commercial papain activated by HCN. On the other hand, the ripe fruits contain no activator, but the juice can be activated by HCN or by the juice of unripe fruits. The fully ripe papaya fruits yield no milky juice. Extracts from seed are fully activated. Therefore it appears that in the earlier stages of development of papaya fruits, the protease can hydrolyze higher and lower proteins, but with increasing ripeness confines its activity to the higher ones. The same relation between ripeness and condition of activation is shown in the pineapple; but due to the structure of the pineapple, it was impossible to distinguish between the activator and inactivated proteases. The name phytokinase is proposed for such natural activators of fruit proteases. Besides the simple system of proteases in the milky juices of plants there is another group of plant proteases, such as those in pumpkin and cucumber, the action of which is checked by HCN.