Quantitative assay for production of
L-asparaginase by isolated bacterial cultures:
The quantitative estimation of enzyme
activity was done with selected culture i.e. E. coli
isolates VRY-8, VRY-14 & VRY-15. Asparaginase
activity was measured by method of Mashburn &
Wriston (1963). The rate of hydrolysis of L-asparagine
was determined by measuring the release of ammonia
using Nessler’s reaction. The reaction mixture
contained 0.5 ml of enzyme sample, 0.5 ml of 0.05 M
Tris-HCl buffer (pH 8.6) and 0.5 ml of 0.04 M Lasparagine.
The reaction mixture was incubated at
37°C for 30 min. The enzyme activity was stopped by
the addition of trichloroacetic acid (TCA 10%w/v). The
mixture was then centrifugated at 10,000 rpm for 5
min, and 0.1 ml of the supernatant was taken and to it
3.7 ml of distilled water was added; 0.2 ml of Nessler’s
reagent (Himedia) was added to the reaction tube and
kept at 20°C for 20 min. The absorbance was measured
at 450 nm using spectrophotometer. The amount of
ammonia liberated was calculated using ammonium
standard curve. One unit of L-asparaginase activity is
defined as release of one micromole of ammonia per
hour at 37°C and pH 8.6.