Inhibition of Escherichia coli respiratory enzymes by the lactoperoxidase-hydrogen peroxide-thiocyanate antimicrobial system

Abstract

Aims: The lactoperoxidase-hydrogen peroxide-thiocyanate antimicrobial system (LPAS) is known to inhibit bacterial respiration. In the present study, several respiratory enzymes of Escherichia coli were compared in terms of their susceptibility to the LPAS. Methods and Results: Exposure of E. coli to the LPAS, upon which 99á6% of the bacteria were killed, resulted in the following percentage of inactivation of substrate-speci®c membrane oxidases: succinate (94á2%) > NADH (84á6%) > glycerol-3-phosphate (67á8%) > DL DL-lactate (64á1%). With the same treatment, substrate-speci®c membrane dehydrogenases were inactivated as follows: succinate (99á1%) > DL DL-lactate (53á8%) > glycerol-3-phosphate (45á0%) > NADH (36á8%). Terminal oxidase, however, measured using a ubiquinone analogue (2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone) after reduction, was only 21á4% inactivated by the LPAS. Conclusions: These data suggest that dehydrogenases are the primary targets of the LPAS in the respiratory chain of E. coli. Signi®cance and Impact of the Study: This study has determined for the ®rst time the primary targets of LPAS in the bacterial respiratory chain.

Susceptibility of Helicobacter pylori and its urease activity to the peroxidase-hydrogen peroxide-thiocyanate antimicrobial system

“…This concentration of SCN À is within the range reported in human saliva samples (1:21 AE 0:66 m for resting condition and 0:84 AE 0:48 m for stimulated condition) [31]. In a previous study, it was observed that the LPO system with a composition similar to that used in this study (0.66 mM SCN À , 0.6 mM H 2 O 2 and bovine LPO 8 mg=L in 50 mM phosphate buffer, pH 6.6) yielded OSCN À at concentrations of 171 and 48 ìM at 5 and 60 min after the start of the reaction, respectively [30]. These concentrations of OSCN À are also within the range of that reported in human parotid saliva samples collected directly from Stensen's duct (range 10±210 ìM, av- The results of the present study show that the peroxidase system inactivates ureases from H. pylori and Jack bean.…”

“…These enzymes catalyse the hydrogen peroxide (H 2 O 2 )-dependent oxidation of thiocyanate (SCN À ) to yield the hypothiocyanite anion (OSCN À ) with inhibitory activity against a wide variety of micro-organisms including gram-positive and gram-negative bacteria, fungi and viruses [19±23]. The product, OSCN À , reacts with microbial sulph-hydryls [24] and inhibits various cellular processes such as glycolysis [25,26], membrane transport of sugars and amino acids [27,28] and respiration [29,30]. It has been estimated that human saliva samples under resting and stimulated conditions contain OSCN À at average concentrations of 61 and 34 ìM, respectively [31].…”

Expression and characterization of bovine lactoperoxidase by recombinant vaccinia virus

“…However, the replication of vv/bLPO at a moi of 5 PFU/cell was not inhibited by antiviral activity of recombinant bLPO, because LPO catalyzes oxidation of endogenous thiocyanate (SCN -) to produce hypothiocyanate (OSCN -) only in the presence of hydrogen peroxide (H 2 O 2 ). These products have a broad-spectrum antimicrobial and antiviral activity (Shin et al 2001(Shin et al , 2005. Therefore due to the absence of thiocyanate (SCN -) and/or hydrogen peroxide (H 2 O 2 ) the replication of recombinant virus is not inhibited by recombinant bLPO.…”

Inhibition ofEscherichia colirespiratory enzymes by short visible femtosecond laser irradiation

“…The numbers of viable bacteria were counted as the numbers of colonies formed on LB plates. The membrane fractions were prepared by sonicating bacterial cells with cell disruptor following the protocol used by Lönnerdal B.et al [15]. The protein concentration was determined by Bradford assay (Bioshop).…”