. 1998 Dec;42(12):3117–3122. doi: 10.1128/aac.42.12.3117

TABLE 2.

Kinetic parameters (± SD) for the initial (V_o) and steady-state (V_ss) phases of hydrolysis of β-lactams by OXA-10 and -16 β-lactamase in 0.1 M phosphate buffer (pH 7.0) at 37°C

Substrate	OXA-10
	V_ss			V_o			Initial β-lactamase concn^b (μM)
	K_m (μM)	k_cat (s⁻¹)	k_cat/K_m^a	K_m (μM)	k_cat (s⁻¹)	K_cat/K_m	Initial β-lactamase concn^b (μM)
Penicillin G	63 ± 6^c	89 ± 10	1,410	-^e	-	-	0.61
Ampicillin	235 ± 30	5,590 ± 30	2,500	77 ± 9	531 ± 12	6,900	0.3
Carbenicillin	195 ± 13	31 ± 1	159	370 ± 44	126 ± 5	340	0.61
Oxacillin	222 ± 16	608 ± 10	2,740	96 ± 8	660 ± 10	6,870	0.61
Cloxacillin	2,640 ± 323	530 ± 36	196	1,110 ± 100	2,680 ± 150	2,420	1.21
Cephaloridine	2,340 ± 300	79 ± 8	33	395 ± 83	39 ± 3	98	0.61
Cephalothin	38 ± 2	6 ± 0.1	158	-	-	-	3.03
Cefotaxime	346 ± 19	9 ± 0.2	26	-	-	-	2.43
Ceftriaxone	55 ± 2	3 ± 0.3	54	-	-	-	12.13
Ceftazidime	ND^d	ND	ND	-	-	-	12.13

OXA-16
V_xx			V_o			Initial β-lactamase concn^b (μM)
K_m (μM)	k_cat (s⁻¹)	k_cat/K_m^a	K_m (μM)	k_cat (s⁻¹)	k_{cat_/}K_m^a	Initial β-lactamase concn^b (μM)
65 ± 1	48 ± 1	738	<20	>60	-	1.74
205 ± 21	97 ± 4	473	142 ± 31	163 ± 8	1,150	0.58
129 ± 32	17 ± 1	132	150 ± 26	69 ± 4	460	0.82
960 ± 159	411 ± 36	428	660 ± 120	455 ± 35	758	0.44
2,080 ± 333	264 ± 25	127	1,120 ± 261	1,200 ± 137	1,070	0.82
424 ± 40	21 ± 1	50	379 ± 61	30 ± 2	79	0.82
32 ± 3	3 ± 1	94	-	-	-	1.74
346 ± 43	6 ± 0.5	17	157 ± 40	10 ± 0.5	64	0.82
36 ± 2	1.4 ± 0.5	39	-	-	-	1.74
ND	ND	ND	ND	ND	ND	1.74

(k_cat/K_m) × 1,000, in micromolar⁻¹ second⁻¹.

Concentration of the stock enzyme from which samples were taken to start the assays before dilution with substrate.

Cases where V_o and V_ss were significant are indicated in boldface.

ND, hydrolysis not detected.

-, linear kinetics, so V_o corresponds to V_ss.