TABLE 3.

Kinetic parameters of B. pseudomallei β-lactamases^a

Substrate	PenA	Vmax	Km	kcat	kcat/Km
Nitrocefin	316a	159 ± 7.4	10.9 ± 2.1	4.91	446
	316c	67.6 ± 4.2	3.34 ± 0.7	1.01	303
	392f	351 ± 7.2	38 ± 2.1	46.2	1,214
AMP	316a	1,316 ± 114	126 ± 29.5	0.18	1.45
	316c	NM	13.8	0.04	2.74*
	392f	4,087 ± 601	1,051 ± 237	37.2	35.4
AMX	316a	NM	2.22*	NM	NM
	316c	NM	0.88*	0.09	96.9*
	392f	NM	74.6*	NM	NM
CFZ	316a	1,024 ± 106	59.5 ± 17.8	21.35	359
	316c	168 ± 5.9	12.6 ± 1.8	0.63	50
	392f	2,390 ± 383	255 ± 52.8	78.6	307
FOX	316a	NH	NR	NH	NH
	316c	NM	15.4*	0.02	1.02*
	392f	NH	NR	NH	NH
CRO	316a	1,514 ± 389	287 ± 117	63.1	219
	316c	253 ± 29.4	29.4 ± 8.5	0.95	32.4
	392f	802 ± 128	138 ± 34.4	26.3	191
CAZ	316a	NM	NR	NM	NM
	316c	NM	10.3*	0.02*	2.33*
	392f	NM	NR	NM	NM
ATM	316a	1,645 ± 211	179 ± 61.4	3.2	17.9
	316c	NM	48.1*	0.15*	3.2*
	392f	1,939 ± 144	336 ± 51.9	17.6	52.5
IPM	316a	NH	NR	NH	NH
	316c	NH	NM**	NH	NM**
	392f	NH	NR	NH	NH
CLA	316a	ND	0.61*	ND	ND
	316c	ND	17.7*	ND	ND
	392f	ND	3.18*	ND	ND

^aUnits are μMs⁻¹ for Vmax, μM for Km, s⁻¹ for kcat, and mM⁻¹s⁻¹ for kcat/Km. CLA; clavulanic acid. Other antibiotic abbreviations are as listed in Table 1. NR, antibiotic was not recognized by that particular enzyme; NM, the rate of hydrolysis is too slow to be measured accurately; ND, not determined; NH, hydrolysis was not detected after 30 minutes. ∗, Ki was used as Km ; ∗∗, the enzyme was completely inactivated by imipenem and no nitrocefin hydrolysis was detected.