Activity of peptidase in tobacco-leaf tissue in relation to senescence.

1. Peptidase extracted with buffer at pH5.2 from small samples of tobacco-leaf tissue was assayed by measuring the alpha-amino nitrogen liberated from gelatin at 40 degrees in 1hr. The rate of hydrolysis was constant during the digestion. 2. The inclusion of sodium thioglycollate (60mm) in the extracting medium increased the activity of the peptidase. 3. As the major products of hydrolysis were peptides, the enzyme is an endopeptidase. 4. The decrease in protein observed in leaves with increasing physiological age and with time after harvest is correlated with increase in specific activity of peptidase in extracts from the leaves.