Table 3.

Effect of detergents on Nk activity

Detergent	Remaining activity (%) at concentration (%) of
	0.2	0.5	1
Triton X-100	113 ± 0	114 ± 1.2	112 ± 2.7
Tween 20	141 ± 6.2	122 ± 0	118 ± 2.4
Tween 80	138 ± 0.6	139 ± 4.1	138 ± 0.3
SDS	66 ± 3.8	13 ± 1.5	11 ± 0.3

0.6 μg of the Nk was incubated in 50 mM Na-phosphate buffer pH 8 at 30°C for 1 h in the presence of 0.2, 0.5 or 1% (w/v) of various detergents. The Nk activity was measured with 1 mM Suc-AAPF-pNA as a substrate at pH 9 and 65°C.