Lactoperoxidase peroxide system

The excretion of thiocyanate into milk is limited. However, thiocyanate may occasionally be added to dairy milk to activate the lactoperoxidase peroxide system, and thereby retard bacterial growth in raw milk. In India, ingestion of such milk led to impairment of thyroid function (Banerjee et al., 1997a), whereas a short-term study from Sweden did not find any effect (Dahlberg et ai, 1984). 

Reiter, B., Marshall, V.M.E., Bjorck, L., and Rosen, C.G. 1976. Nonspecific bactericidal activity of the lactoperoxidase-thiocyanate-hydrogen peroxide system of milk against Escherichia coli and some Gram-negative pathogens. Infect. Immun. 13, 800—807. 

Figure 12.6 The immobilized glucose oxidase/lactoperoxidase system radioiodinates proteins through the intermediate formation of hydrogen peroxide from the oxidation of glucose. H2O2 then reacts with iodide anions to form reactive iodine (I2). This efficiently drives the formation of the highly reactive H2OI+ species that is capable of iodinating tyrosine or histidine residues (see Figure 12.2).

Bjorck, L. and Claesson, O. 1979. Xanthine oxidase as a source of hydrogen peroxide for the lactoperoxidase system in milk. J. Dairy Sci. 62, 1211-1215. 

Control experiments should be included in order to determine whether the cells under investigation contain endogenous systems capable of catalyzing iodination or iodide oxidation. These controls should include a sample in which the enzyme lactoperoxidase is omitted and one to which peroxide is not added. 

III H) 1910-1 Lotka, A. Contribution to the Theory of Periodic Reactions, J. Phys. Chem. vol. 14, (III C) 1975 Marek, M., Svobodova, E. Nonlinear Phenomena in Oscillatory Systems of Homogeneous Reactions-Experimental Observations, Biophysical Chemistry, vol. 3, 263—273 (III A) 1974 Matsuzaki, I., Nakajima, T., Liebhafsky, H. A. The Mechanism of the Oscillatory Decomposition of Hydrogen Peroxide by the I2-IO3-couple, Chem. Letters (Japan) 1463-1466 (IIT O) 1969 Nakamura, S., Yokota, K., Yamazaki, I. Sustained Oscillations in a Lactoperoxidase, NADPH and 02 system Nature vol. 222, 794... 

Hydrogen peroxide is generated by the lactic acid bacteria in the presence of oxygen. Hydrogen peroxide is bactericidal but is mainly important as one of the components of the lactoperoxidase system (Lindgren and Dobrogosz, 1990). 

The lactoperoxidase enzyme is present in raw milk. This enzyme forms part of the lactoperoxidase system, which also includes thiocyanate and hydrogen peroxide produced by aerobic microorganisms in milk. The lactoperoxidase system produces an antimicrobial substance that exerts a preservative effect in raw milk (Blom and Mprtvedt, 1991). 

After formation of the antigen-antibody complex, and removal of excess of reagents, light was produced by reacting the complex with microperoxidase / hydrogen peroxide, or lactoperoxidase/hydrogen peroxide (the latter oxidative system was used only in the biotin chemiluminescent immunoassay). 

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