Figure 1.
Chemical structure of β-lactamase inhibitors.
Different inhibitors used in the study are (a) clavulanic acid, (b) tazobactam, (c) sulbactam, and (d) ZINC03787097.
Table 1.
MICs of β-lactams alone or in combination with inhibitors for E. coli DH5α transformed with recombinant blaCTX-M-15 from Enterobacter cloacae.
Figure 2.
Determination of IC50 values for different inhibitors.
The residual activity of CTX-M-15 after 5 minutes pre-incubation with varying concentrations of different inhibitors as monitored by the hydrolysis of 100 µM nitrocefin.
Table 2.
Concentration of the inhibitors required to reduce the enzyme activity by 50%.
Table 3.
Steady-state kinetic parameters of CTX-M-15 from Enterobacter cloacae.
Figure 3.
Effect of various inhibitors on the kinetics of CTX-M-15.
Variation of inactivation rate constant (ki) versus different inhibitor concentrations for CTX-M-15 from clinical Enterobacter cloacae strain EC-15. The dotted line represents the best fit (linear regression) among the data points.
Table 4.
Effect of various inhibitors on the steady-state kinetic parameters of CTX-M-15.
Figure 4.
Molecular docking of various inhibitors at the active site of CTX-M-15.
Panel (A) shows molecular docking of clavulanic acid (red), sulbactam (green), tazobactam (yellow) and screened compound ZINC03787097 (blue) at the active site of CTX-M-15 from clinical strain of Enterobacter cloacae (EC-15). Panel (B) represents close view of interacting amino acids in which dashed lines represent hydrogen bonds. Ambler positions of amino acids are Ser-73 (Ser-42), Tyr-108 (Tyr-77), Ser-133 (Ser-102), Asn-135 (Asn-104), Asn-173 (Asn-141), Gly-239 (Gly-208), Ser-240 (Ser-209), Thr-218 (Thr-188).