Table 1.

Kinetic parameters for OXA-23, OXA-239 and other variants

	kcat (s−1)	KM or Ks (μM)	kcat/KM (μM−1·s−1)
OXA-23a
ampicillin	460 ± 10	82 ± 9	5.7 ± 0.6
cefotaxime	5.5 ± 0.1	340 ± 30	0.016 ± 0.002
cefepime	20 ± 1	1100 ± 200	0.018 ± 0.003
ceftriaxone	0.016 ± 0.001	3.7 ± 0.5	0.0044 ± 0.0007
ceftazidime	< 0.01	NA	NA
doripenem	0.028 ± 0.003	0.018 ± 0.002b	1.5 ± 0.3
imipenem	0.49 ± 0.01	0.20 ± 0.02b	2.4 ± 0.3
aztreonam	0.24 ± 0.01	2400 ± 100	0.00010 ± 0.00001
OXA-239
ampicillin	99 ± 3	22 ± 3	4.5 ± 0.5
cefotaxime	5.0 ± 0.3	12 ± 3	0.43 ± 0.10
cefepime	34 ± 1	200 ± 20	0.18 ± 0.02
ceftriaxone	0.047 ± 0.004	0.49 ± 0.07b	0.097 ± 0.016
ceftazidime	2.8 ± 0.1	600 ± 40	0.0050 ± 0.0003
doripenem	0.017 ± 0.002	0.036 ± 0.010b	0.48 ± 0.14
imipenem	1.3 ± 0.1	13 ± 3b	0.10 ± 0.03
aztreonam	0.43 ± 0.01	20 ± 2	0.022 ± 0.002
OXA-23 S109L
ampicillin	150 ± 10	140 ± 10	1.1 ± 0.1
cefotaxime	NA	> 400	NA
doripenem	0.017 ± 0.001	< 0.010b	NA
imipenem	0.24 ± 0.01	0.23 ± 0.02b	1.0 ± 0.1
aztreonam	< 0.05	NA	NA
OXA-23 D222N
ampicillin	310 ± 10	34 ± 2	9.0 ± 0.5
cefotaxime	1.9 ± 0.1	33 ± 3	0.058 ± 0.005
doripenem	0.027 ± 0.001	0.011 ± 0.001b	2.5 ± 0.2
imipenem	1.1 ± 0.1	12 ± 3b	0.098 ± 0.023
aztreonam	0.43 ± 0.01	390 ± 40	0.0011 ± 0.0001
OXA-23 P225Sa
ampicillin	150 ± 10	12 ± 1	12 ± 1
cefotaxime	3.2 ± 0.2	100 ± 20	0.031 ± 0.006
ceftazidime	1.4 ± 0.1	1400 ± 200	0.0010 ± 0.0002
doripenem	0.026 ± 0.002	0.027 ± 0.005b	1.0 ± 0.2
imipenem	0.39 ± 0.01	0.20 ± 0.02b	1.9 ± 0.2
aztreonam	0.79 ± 0.03	13 ± 2	0.061 ± 0.010
OXA-23 D222N/P225S
ampicillin	140 ± 2	30 ± 1	4.5 ± 0.2
cefotaxime	1.5 ± 0.1	23 ± 3	0.066 ± 0.008
doripenem	0.021 ± 0.001	0.071 ± 0.007	0.30 ± 0.03
imipenem	1.1 ± 0.1	11 ± 1b	0.10 ± 0.01
aztreonam	0.62 ± 0.01	21 ± 2	0.030 ± 0.002

^aOXA-23 and OXA-225 values (except for cefepime) were previously reported in Mitchell et al. Biochemistry. 54, 1976–1987b

^bFor variants with very low K_m values, K_s values were calculated by competition with a reporter substrate

NA: not applicable