Table 2.

Stabilities and activities of purified subtilisin E variants

Variant	t1/2 at 65°C*, min	Tm†, °C	Specific activity, unit/mg‡
Wild type	5.1  ±  0.2	68.1	17.2  ±  0.1
1E2A	42.8  ±  0.1	74.4	33.7  ±  0.7
V93I	5.0  ±  0.1	68.1	21.6  ±  0.2
N109S	5.2  ±  0.1	68.2	16.1  ±  0.4
N181D	16.5  ±  0.6	71.8	18.0  ±  0.6
N218S	10.9  ±  0.1	71.3	38.6  ±  0.6
N218S + N181D	49.9  ±  0.8	74.6	38.4  ±  0.1

^*Half-life of thermoinactivation, pH 8.0, 10 mM CaCl₂. 

^†Melting temperature, as measured by differential scanning calorimetry, pH 8.0, 1 mM CaCl₂. 

^‡Specific activity toward suc-AAPF-pNA at pH 8.0.