Protease assay: The enzyme extract suitably diluted,
was mixed with 50mM glycine - NaOH buffer (pH 9) to
make 1 ml volume. 1ml of 1% casein (substrate) was added
and incubated for 10 min at 60°C. The reaction was stopped
by addition of 0.5 ml TCA (20%, w/v). The mixture was
allowed to stand at room temperature for 30 min and filtered.
1 ml of the filtrate was mixed with 5 ml of 0.5M Na2CO3
solution. 0.5 ml of Folin & Ciocalteu’s (phenol reagent)
reagent was added and kept in dark to develop the blue color.
It was estimated spectrophotometrically at 660nm against
tyrosine as standard. One unit of protease activity was
defined as the amount of enzyme required to liberate1 g
tyrosine per milliliter in 1 min under the experimental
conditions used.