Beiträge zur Aktivierung pflanzlicher Proteinasen.

Abstract

Gelatin hydrolysis by papain is activated by Fe" only when the enzyme is contaminated by an inhibitory substance "X." Papain precipitated from water solution by alcohol is free from X and is not activated by Fe". The inhibition caused by readdition of X from the mother liquor is then removable by Fe". The reaction is probably a reduction of X by Fe" although ascorbic acid or HaS is ineffective. In the presence of Fe" the amount of cystein necessary for maximal activation of papain is greatly reduced. Papain containing X will attack Witte peptone in the presence of Fe". Witte peptone in the presence of ascorbic acid slowly acquires attack-ability by papain. HCN activates papain only indirectly, by reducing S-S compounds in enzyme or substrate. Pd (on charcoal) inhibits papain, but in H2 atmosphere this inhibition is largely removed. There is no real activation of papain by Pd and H2. The natural activator of bromelin is not removed by alcohol, and therefore cannot be cystein or SH-glutathione. Bromelin preparations contain no X but seem otherwise identical with papain. Yeast proteinase also contains no X and its activity is also not affected by removal of SH compounds.