Human serum paraoxonase-1 (hPON1): in vitro inhibition effects of moxifloxacin hydrochloride, levofloxacin hemihidrate, cefepime hydrochloride, cefotaxime sodium and ceftizoxime sodium

Figures & data

Figure 1. SDS-PAGE analysis of purified hPON1. Lane (A) is standard proteins (kD): Bovine serum albumin (66.000), aldolase (47.500), triosephosphate isomerase (32.000) and soy bean trypsin inhibitor (24.000). Lane B contains a human serum sample.

Figure 2. In vitro effect of antibacterial drugs: (a) moxifloxacin hydrochloride, (b) levofloxacin hemihidrate, (c) cefepime hydrochloride, (d) cefotaxime sodium and (e) ceftizoxime sodium at five different concentrations on hPON1 activity.

Figure 3. K_i graphs for paraoxonase from human serum. (a), (b), (c) and (d) Lineweaver–Burk graphs in five different substrate (paraoxon) concentrations and three different (a) moxifloxacin hydrochloride, (b) levofloxacin hemihidrate, (c) cefepime hydrochloride, (d) cefotaxime sodium and (e) ceftizoxime sodium concentrations for determination of K_i.

Figure 4. Schematic representation for the interaction of moxifloxacin hydrochloride (a) with the hPON1 active site.

Table 1. Summary of the hPON1 purification procedure.

Purification step	Activity (EU/ml)	Total volume (ml)	Protein (mg/ml)	Total protein (mg)	Total activity (EU)	Specific activity (EU/mg)	Yield (%)	Purification factor
Serum	111.5	25	5.58	139.6	2788.4	20	100	1
Ammonium sulpateprecipitation (60-80%)	114.5	18	4.01	72.2	2060.1	28.5	73.9	1.4
DEAE-Sephadex A50 anion exchange chromatography	117.7	12	0.17	2.1	1412.8	672.9	50.7	33.7
Sephadex G-200 gel filtration chromatography	119.2	8	0.03	0.2	953.5	4612.4	34.2	230.9

Table 2. IC₅₀, K_i values and inhibition types.

Inhibitors	IC50 (mM)	R^2 values of IC50	Average values of Ki (mM)	Type of inhibition
Moxifloxacin hydrochloride	1.839	0.9898	2.641 ± 0.040	Competitive
Levofloxacin hemihidrate	3.959	0.9988	5.525 ± 0.817	Noncompetitive
Cefepime hydrochloride	21.115	0.9946	35.092 ± 1.093	Noncompetitive
Cefotaxime sodium	152.161	0.9918	252.762 ± 5.749	Noncompetitive
Ceftizoxime sodium	311.915	0.9960	499.244 ± 10.149	Noncompetitive