Determination of protease activity of plant roots

The colorimetric method described by Charney and Tomarelli (1974) for the assay of the proteolytic activity in the duodenal juice was adapted to measuring protease activity of roots. Diazotized casein served as substrate and the amount of degraded azocasein was measured colorimetrically. A linear relationship between the incubation time or concentration of the enzyme (roots) and the amount of the hydrolyzed substrate was found. The rate increase of the enzyme reaction was proportional to enzyme concentration up to 1 g roots and incubation time of 3 h, and up to 0.5 g of roots and incubation time of 4 h. The optimum of the protease activity was at pH 8.2–8.6.