Identification of a New Serine Alkaline Peptidase from the Moderately Halophilic Virgibacillus natechei sp. nov., Strain FarD^T and its Application as Bioadditive for Peptide Synthesis and Laundry Detergent Formulations

Table 3

Effects of synthetic and natural inhibitors, with a molar ratio of [inhibitor]/[enzyme] was 100, as well as group-specific reagents and chelating agents, on SAPV stability. SAPV activity assayed without inhibitor or reducing agent was taken as control (100%). The nontreated and dialyzed SAPV was considered as 100% for metal ion assay. Residual SAPV activity was measured at pH 9 and 60°C.

Compound	Concentration	Residual peptidase activity (%)^a
None	—	100 ± 2.5
PMSF	5 mM	0 ± 0.0
DFP	2 mM	0 ± 0.0
SBTI	3 mg/mL	96 ± 1.9
TLCK	1 mM	104 ± 2.6
TPCK	1 mM	108 ± 2.8
Benzamidine	5 mM	102 ± 2.6
DTNB	10 mM	117 ± 3.0
LD-DTT	1 mM	109 ± 2.6
2-ME	5 mM	113 ± 2.8
NEM	2 mM	100 ± 2.5
Iodoacetamide	5 mM	100 ± 2.5
Leupeptin	2 mM	111 ± 2.8
Pepstatin A	1 mM	102 ± 2.7
MIA	50 µM	97 ± 2.1
EPNP	5 mM	104 ± 2.6
1,10-Phenanthroline monohydrate	10 mM	105 ± 2.7
EDTA	10 mM	86 ± 1.3
EGTA	2 mM	74 ± 1.2
Ca^2+ (CaCl2)	2 mM	290 ± 7
Fe^2+ (FeCl2)	2 mM	210 ± 4.8
Cu^2+ (CuCl2)	2 mM	125 ± 2.8
Mn^2+ (MnCl2)	2 mM	100 ± 2.5
Mg^2+ (MgCl2)	2 mM	100 ± 2.5
Zn^2+ (ZnCl2)	2 mM	120 ± 2.9
Co^2+ (CoCl2), Hg^2+ (HgCl2), or Cd^2+ (CdCl2)	2 mM	0 ± 0.0

^aValues represent the means of three replicates, and ± standard errors are reported. SBTI: soybean trypsin inhibitor; TLCK: Nα-p-tosyl-L-lysine chloromethyl ketone; TPCK: Nα-p-tosyl-L-phenylalanine chloromethyl ketone; DTNB: 5,5′-dithio-bis-2-nitro benzoic acid; NEM: N-ethylmalemide; MIA: monoiodoacetic acid; EPNP: 1,2-epoxy-3-(p-nitrophenoloxy) propane.