Table 2.

Effects of protease inhibitors and denaturants on recombinant AprX-SK37 activity using azocasein as a substrate^a

Characteristic	Inhibitors	Concentration	Remaining activity (%)
Serine protease inhibitor	Leupeptin	10 mM	100.7
	SBTI	0.4 mg/ml	100.9
	TLCK	10 mM	99.4
	TPCK	10 mM	99.9
	PMSF	1 mM	89.2
		10 mM	1.0
Metalloprotease inhibitor	EDTA	0.5 mM	78.1
		1 mM	64.2
		5 mM	1.4
	Imidazole	0.5 M	82.4
	L-Histidine	0.5 M	108.1
Cysteine protease inhibitor	IAA	0.1 M	98.0
	NEM	0.1 M	114.2
	E64	1 mM	99.2
Aspartic protease inhibitor	Pepstatin A	1 mM	102.1
Amino peptidase inhibitor	Bestatin	2 mM	102.6
Denaturants	Substances	Concentration	Remaining activity (%)
H-bond breaker	Urea	1M	20.8
		2M	0.0
Detergent	SDS	0.5%	0.0
		1.0%	0.0
Reducing agents	DTT	1 mM	38.5
		10 mM	2.3
		20 mM	0.1
	BME	1 mM	64.7
		10 mM	41.9
		20 mM	14.1

^a The enzymatic activity was determined at pH 9.5 and 55°C in the presence of 5 mg/ml substrate and 5 mM CaCl₂. The experiment was performed in triplicate, and standard errors from the means were within 15% of the reported values.