Antibacterial Activity of the Lactoperoxidase System: A Review

Abstract

The lactoperoxidase (LP) system is a naturally occurring system which was first discovered in raw milk. Different groups of bacteria show a varying degree of resistance to the LP system. Gram-negative catalase-positive organisms, such as pseudomonads, coliforms, salmonellae, and shigellae, are inhibited by the LP system. Depending on the medium pH, temperature, incubation time, cell density, and the particular donor, these microorganisms may be killed. It has been shown that the LP system can increase storage times of raw milk by delaying growth of psychrotrophs; perhaps this method could be used to extend the shelf life of other foods.

Thiocyanate Modulates the Catalytic Activity of Mammalian Peroxidases

“…LPO is a monomeric single polypeptide chain with a molecular mass of 78.5 kDa (20 -23). LPO has been identified as an antimicrobial agent within exocrine gland secretions such as milk, saliva, and tears through the oxidation of thiocyanate by H 2 O 2 to yield the intermediary oxidation product hypothiocyanite (OSCN Ϫ ) (24,25). The properties of the heme in MPO, EPO, and LPO have been characterized by a wide variety of spectroscopic techniques, including optical absorption, stopped-flow, electron paramagnetic resonance, and resonance Raman spectroscopy (26 -37).…”

High Dissociation Rate Constant of Ferrous-Dioxy Complex Linked to the Catalase-like Activity in Lactoperoxidase

“…Organic and inorganic compounds may also serve as substrates enhancing the catalytic cycle of mammalian peroxidases by accelerating Compound II (LPO-Fe(IV)-O) formation and subsequent decay to the ground state, which is thought to be the rate-limiting step in the classic peroxidase cycle (12-17, 28 -32). The enzyme has been identified as an antimicrobial agent in milk, saliva, and tears and is produced by goblet cells and submucosal glands that form airway mucus secretions (33,34). A variety of evidence suggests that the peroxidase heme prosthetic group is involved in a wide range of important processes through its catalytic reactions that include binding, transport, and activation of oxygen, as well as deactivation of reactive oxygen compounds, oxidation/reduction reactions, and electron transport (17,19,35).…”

Effect of the lactoperoxidase system on proteolysis and physicochemical changes in ultra high temperature milk during storage

“…These data are confirmed by extracellular proteolytic activity (Table 2) control and activated LPS UHT milks are observed during all storage period; these differences reached about average values of 0.13 pH unit and 3ºD for acidity. Indeed, LP system, activated in refrigerated raw milk, affect growth of psychrotrophic Gram negative bacteria (Kamau et al, 1984;Wolfson and Sumner, 1993), as, it has the ability to catalyse the oxidation of thiocyanate by hydrogen peroxide with the production of the antibacterial hypothiocyanite (OSCN -) and other intermediates such as, thiocyanogen (SCN 2 ). These compounds, which can be further oxidized to end-products that are harmless to humans, have the ability to reduce bacterial growth by damaging the cell membranes and inhibiting the synthesis of proteins such as, DNA and RNA (Seifu, 2005).…”