Marked enhancement of Acinetobacter sp. organophosphorus hydrolase activity by a single residue substitution Ile211Ala

Bioresources and Bioprocessing

Table 2 Specific activities and kinetic parameters of wild-type AbOPH and its variants

Enzymes	Specific activity (U/mg)	K _M (μM)	k _cat (min⁻¹)	k _cat/K _M (min⁻¹ μM⁻¹)
AbOPH	ND	ND	ND	–
AbOPH_I211A	1.060 ± 0.023	103 ± 14	93.2 ± 3.2	0.90
AbOPH_L156M	0.0115 ± 0.0010	45.5 ± 5.6	0.862 ± 0.031	0.018
AbOPH_H268L	0.0104 ± 0.0011	56.7 ± 7.0	0.804 ± 0.030	0.013

Specific activities of purified enzymes were measured toward 0.5 mM MP
The kinetic parameters were determined by measuring purified enzyme activities toward MP at concentration from 0.01 to 1 mM and fitting data to the Michaelis–Menten equation. All enzymatic assays were performed at least in triplicate and average values were adopted
ND no enzymatic activity was detected except spontaneous hydrolysis, in spite of the high enzyme loading (2 mg/mL)