Table 2.
Effect of buffer type and pH on the catalytic activity of lyophilized subtilisin Carlsberg samples
| Buffer type | Relative
initial rate, %
|
|
|---|---|---|
| pH 5.0 | pH 8.5 | |
| Na-phosphate | 12* | 100 |
| NaOOCH | 101 | 117 |
| NH4-phosphate | 1.0 | 3.3 |
| NH4OOCH | 8.4 | 8.7 |
The enzyme was lyophilized from buffer of the type and pH shown. The solvent mixture and enzyme powder were equilibrated separately to aw 0.75. The reaction was carried out at 23°C with shaking at 500 oscillations per minute. The rates were expressed in terms of the content of subtilisin in each preparation (correcting for the different amounts of residual salt after drying the enzyme from different buffers) and then were normalized to the sample prepared from pH 8.5 Na-phosphate buffer, 10.7 nmol⋅min−1 (milligrams of salt-free subtilisin)−1.
*
Determined by Yang et al. (9) under similar conditions.