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


RESULTS
Exposure of E. coli to the LPAS, upon which 99.6% of the bacteria were killed, resulted in the following percentage of inactivation of substrate-specific membrane oxidases: succinate (94.2%) > NADH (84.6%) > glycerol-3-phosphate (67.8%) > DL-lactate (64.1%). With the same treatment, substrate-specific membrane dehydrogenases were inactivated as follows: succinate (99.1%) > DL-lactate (53.8%) > glycerol-3-phosphate (45.0%) > NADH (36.8%). Terminal oxidase, however, measured using a ubiquinone analogue (2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone) after reduction, was only 21.4% inactivated by the LPAS.


CONCLUSIONS
These data suggest that dehydrogenases are the primary targets of the LPAS in the respiratory chain of E. coli.


CONCLUSIONS
This study has determined for the first time the primary targets of LPAS in the bacterial respiratory chain.
Shin
K
K
Nutritional Science Laboratory, Morinaga Milk Industry Co. Ltd, Kanagawa, Japan.
Hayasawa
H
H
Lönnerdal
B
B
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015169:Colony Count, Microbial; D004338:Drug Combinations; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007784:Lactoperoxidase / Q000494:pharmacology; D008565:Membrane Proteins / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D013861:Thiocyanates / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D004338:Drug Combinations; D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D013861:Thiocyanates; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D007784:Lactoperoxidase; C031760:thiocyanate