Purification of lactoperoxidase from bovine milk and investigation of the kinetic properties

Antimicrobial Activity of Films and Coatings Containing Lactoperoxidase System: A Review

The production of safe and healthy foodstuffs is considered as one of the most important challenges in the food industry, and achieving this important goal is impossible without using various processes and preservatives. However, recently, there has been a growing concern about the use of chemical preservatives and attention has been focused on minimal process and/or free of chemical preservatives in food products. Therefore, researchers and food manufacturers have been induced to utilize natural-based preservatives such as antimicrobial enzymes in their production. Lactoperoxidase, as an example of antimicrobial enzymes, is the second most abundant natural enzyme in the milk and due to its wide range of antibacterial activities, it could be potentially applied as a natural preservative in various food products. On the other hand, due to the diffusion of lactoperoxidase into the whole food matrix and its interaction and/or neutralization with food components, the direct use of lactoperoxidase in food can sometimes be restricted. In this regard, lactoperoxidase can be used as a part of packaging material, especially edible and coating, to keep its antimicrobial properties to extend food shelf-life and food safety maintenance. Therefore, this study aims to review various antimicrobial enzymes and introduce lactoperoxidase as a natural antimicrobial enzyme, its antimicrobial properties, and its functionality in combination with an edible film to extend the shelf-life of food products.

Molecular docking and inhibition profiles of some antibiotics on lactoperoxidase enzyme purified from bovine milk

Antibiotics are generally used for human and veterinary applications to preserve and to control microbial diseases. Milk has a biologically significant enzyme known as lactoperoxidase (LPO) that is a member of peroxidase family. In metabolism, LPO has ability to catalyze the transformation of thiocyanate (SCN^-) to hypothiocyanite (OSCN^-) that is an antibacterial agent and the reaction occurs with hydrogen peroxide. In this work, LPO inhibition effects of some antibiotics including cefazolin, oxytetracycline, flunixin meglumine, cefuroxime, tylosin, vancomycin, chloramphenicol and lincomycin were tested. Among the antibiotics cefazolin was indicated the strongest inhibitory efficacy. The half maximal inhibitory concentration (IC₅₀) and the inhibition constant (K_i) values of cefazolin were found as 8.19 and 34.66 µM, respectively. It was shown competitive inhibition. 5-Methyl-1,3,4-thiadiazol-2-yl moiety activity plays a key role in the inhibition mechanism of cefazolin.Communicated by Ramaswamy H. Sarma.

Immobilization of lactoperoxidase on graphene oxide nanosheets with improved activity and stability

OBJECTIVES

The purpose of this study was to develop a facile and efficient method to enhance the stability and activity of lactoperoxidase (LPO) by using its immobilization on graphene oxide nanosheets (GO-NS).

METHODS

Following the LPO purification from bovine whey, it was immobilized onto functionalized GO-NS using glutaraldehyde as cross-linker. Kinetic properties and stability of free and immobilized LPO were investigated.

RESULTS

LPO was purified 59.13 fold with a specific activity of 5.78 U/mg protein. The successful immobilization of LPO on functionalized GO-NS was confirmed by using dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FT-IR). The overall results showed that the stability of the immobilized LPO was considerably improved compared to free LPO. Apparent K_m and V_max of LPO also indicated that the immobilized enzyme had greater affinity to the substrate than the native enzyme.

CONCLUSIONS

Graphene oxide nanosheets are effective means for immobilization of LPO.

Reactivation of peroxidase activity in human saliva samples by polyphenols

OBJECTIVES

The enzyme lactoperoxidase (LPO), which is released into several body fluids like saliva, is an essential part to maintain the oral bacterial homeostasis by catalysing the oxidation of thiocyanate (SCN^-) to hypo-thiocyanite (^-OSCN). The formation of unreactive redox intermediates (like Compound II) leads to a decreased pseudo-halogenating enzyme activity, which is associated with a higher risk for oral infections. According to former studies with bovine LPO selected flavonoids were tested in respect to their potential to reactivate the enzymatic activity in a more physiological, human salivary system.

DESIGN

Saliva samples from healthy donors were collected and characterized by using several gel staining methods and immunoblotting. Afterwards kinetic measurements were performed by applying the TNB-assay to evaluate the pseudo-halogenating salivary peroxidase (SAPX) activity. The measurements were performed in the presence of excess H₂O₂ to simulate pro-inflammatory conditions. Moreover selected flavonoids or an ethanolic extract of Tormentillae rhizoma were applied to test their regenerating effect on the LPO-derived ^-OSCN production.

RESULTS

Despite the complex protein composition of the collected saliva samples, an SAPX-derived pseudo-halogenating activity could be identified. The ^-OSCN regenerating effects of the tested polyphenols were completely comparable to previous in vitro experiments with bovine LPO. Thus, we could show that phenolic substances are suitable to regenerate the peroxidase activity in human saliva samples after H₂O₂-induced inactivation.

CONCLUSION

The studies provide new insights into the effect of pharmaceutical relevant polyphenols on salivary peroxidase activity and thus, suggest this enzyme as a new target for the prevention and therapy of oral inflammatory diseases.

Purification of lactoperoxidase from bovine whey and investigation of kinetic parameters

BACKGROUND

Lactoperoxidase (LPO) is related to mammalian peroxidase family which contains a wide spectrum of biological activities. Despite the wide studies on the LPO, there is little study has been performed to simplify and shorten the procedure of enzyme purification. The aim of this project was to purify the enzyme through a simple method, and investigating enzyme kinetic parameters.

MATERIALS AND METHODS

LPO was purified from bovine whey through modified method of Yoshida (1990) using two steps of ammonium sulfate precipitation and ion-exchange chromatography. The purity of isolated enzyme was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).

RESULTS

The enzyme was purified 59.13-fold with a recovery of 10.26 having a specific activity of 5.78 U/mg protein and an Rz value of 0.8. The enzyme activity was measured using guaiacol as a chromogenic substrate in phosphate buffer pH 6. SDS-PAGE showed a single bond with molecular weight of 78 kDa. The purified enzyme displayed optimum activity at pH 6 in 30 mM phosphate buffer and at a temperature of 50°C, with a Km value of 178 mM and Vmax 0.63 U/ml.min for guaiacol.

CONCLUSION

Using only one step ion-exchange chromatography, LPO was isolated from bovine whey in high purity.

Inhibition profile of a series of phenolic acids on bovine lactoperoxidase enzyme

Lactoperoxidase (LPO) catalyzes the oxidation of numerous of organic and inorganic substrates by hydrogen peroxide. It has very vital activity in the innate immune system by decreasing or stopping the activation of the bacteria in milk and mucosal secretions. This study's purpose was to investigate in vitro effect of some phenolic acids (ellagic, gallic, ferulic, caffeic, quercetin, p-coumaric, syringic, catechol and epicatechin) on the purified LPO. This enzyme was purified from milk by using different methods such as Amberlite CG-50 resin, CM-Sephadex C-50 ion-exchange and Sephadex G-100 gel filtration chromatography. LPO was purified 28.7-fold with a yield of 20.03%. We found phenolic acids have inhibition effects on bovine LPO enzyme to different concentrations. Our study showed lower concentrations of caffeic acid, ferulic acid and quercetin exhibited much higher inhibitory effect on enzyme, so these three of them were clearly a more potent inhibitor than the others were. All of compounds were non-competitive inhibitors.

Purification of acetylcholinesterase by 9-amino-1,2,3,4-tetrahydroacridine from human erythrocytes

The acetylcholinesterase enzyme was purified from human erythrocyte membranes using a simple and effective method in a single step. Tacrine (9-amino-1,2,3,4-tetrahydroacridine) is a well-known drug for the treatment of Alzheimer's disease, which inhibits cholinesterase. We have developed a tacrine ligand affinity resin that is easy to synthesize, inexpensive and selective for acetylcholinesterase. The affinity resin was synthesized by coupling tacrine as the ligand and L-tyrosine as the spacer arm to CNBr-activated Sepharose 4B. Acetylcholinesterase was purified with a yield of 23.5 %, a specific activity of 9.22 EU/mg proteins and 658-fold purification using the affinity resin in a single step. During purification, the enzyme activity was measured using acetylthiocholine iodide as a substrate and 5,5'-dithiobis-(2-nitrobenzoicacid) as the chromogenic agent. The molecular weight of the enzyme was determined as about 70 kDa monomer upon disulphide reduction by sodium dodecyl sulphate polyacrylamide gel electrophoresis. K(m), V(max), optimum pH and optimum temperature for acetylcholinesterase were found by means of graphics for acetylthiocholine iodide as the substrate. The optimum pH and optimum temperature of the acetylcholinesterase were determined to be 7.4 and 25-35 °C. The Michaelis-Menten constant (K(m)) for the hydrolysis of acetylthiocholine iodide was found to be 0.25 mM, and the V(max) was 0.090 μmol/mL/min. Maximum binding was achieved at 2 °C with pH 7.4 and an ionic strength of approximately 0.1 M. The capacity for the optimum condition was 0.07 mg protein/g gel for acetylcholinesterase.

One-step purification of lactoperoxidase from bovine milk by affinity chromatography

Sulphanilamide was determined to be a new inhibitor of lactoperoxidase (LPO) with an IC(50) of 0.848.10(-5)M. The K(i) for sulphanilamide was determined to be 3.57.10(-5)M and sulphanilamide showed competitive inhibition, which makes it a suitable ligand for constructing a Sepharose 4B-L-tyrosine affinity matrix. The affinity matrix was synthesised by coupling sulphanilamide as the ligand and L-tyrosine as the spacer arm to a cyanogen bromide (CNBr)-activated-Sepharose 4B matrix. Lactoperoxidase was purified 409-fold from the synthesized affinity matrix in a single step, with a yield of 62.3% and a specific activity of 40.9 EU/mg protein. The enzyme activity was measured using ABTS as a chromogenic substrate (pH 6.0). The degree of LPO purification was monitored by SDS-PAGE and its R(z) (A(412)/A(280)) value. The R(z) value for the purified LPO was found to be 0.7. Maximum binding was achieved and K(m) and V(max) values were determined.

In vitroeffects of some anaesthetic drugs on lactoperoxidase enzyme activity

In vitro effects of ketamine and bupivacaine drugs on bovine lactoperoxidase (LPO; E.C. 1.11.1.7) enzyme activity were investigated. Lactoperoxidase was purified with Amberlite CG 50 resin, CM Sephadex C-50 ion-exchange chromatography, and Sephadex G-100 gel filtration chromatography from skimmed bovine milk. Rz(A412/A280) value for the purified LPO was found to be 0.8. Inhibition or activation effects of the drugs on LPO enzyme were determined using 2,2(1)-azino-bis (3-ethylbenzthiazoline-6 sulfonic acid) diammonium salt (ABTS) as a chromogenic substrate at pH = 6.0. The I50 values of ketamine and bupivacaine were 0.29 mM and 0.155 mM, respectively and the K(i) constants for ketamine and bupivacaine were 0.019 +/- 0.031 and 0.015 +/- 0.021 mM, respectively; they were non-competitive inhibitors.

Inactivation of Escherichia coli and Shigella in acidic fruit and vegetable juices by peroxidase systems

AIMS

To study the bactericidal properties of the lactoperoxidase (LPER)-thiocyanate and soybean peroxidase (SBP)-thiocyanate systems at low pH, their efficiency for inactivation of Escherichia coli and Shigella in acidic fruit and vegetable juices, their effect on colour stability of the juices and interaction with ascorbic acid.

METHODS AND RESULTS

Three-strain cocktails of E. coli and Shigella spp. in selected juices were supplemented with the LPER or SBP system. Within 24 h at 20 degrees C, the LPER system inactivated both cocktails by > or = 5 log10 units in apple, 2-5 log10 units in orange and < or = 1 log10 unit in tomato juices. In the presence of SBP, browning was significant in apple juice and white grape juice, slight in pink grape juice and absent in orange or tomato juice. Ascorbic acid protected E. coli and Shigella against inactivation by the LPER system, and peroxidase systems significantly reduced the ascorbic acid content of juices.

CONCLUSIONS

Our results suggest a different specificity of LPER and SBP for SCN-, phenolic substrates of browning and ascorbic acid in acidic juices. The LPER system appeared a more appropriate candidate than the SBP system for biopreservation of juices.

SIGNIFICANCE AND IMPACT OF THE STUDY

This work may open perspectives towards the development of LPER or other peroxidases as biopreservatives in acidic foods.

Characterization of the Oxidase Activity in Mammalian Catalase

Catalase is a highly conserved heme-containing antioxidant enzyme known for its ability to degrade hydrogen peroxide into water and oxygen. In low concentrations of hydrogen peroxide, the enzyme also exhibits peroxidase activity. We report that mammalian catalase also possesses oxidase activity. This activity, which is detected in purified catalases, cell lysates, and intact cells, requires oxygen and utilizes electron donor substrates in the absence of hydrogen peroxide or any added cofactors. Using purified bovine catalase and 10-acetyl-3,7-dihydroxyphenoxazine as the substrate, the oxidase activity was found to be temperature-dependent and displays a pH optimum of 7-9. The Km for the substrate is 2.4 x 10(-4) m, and Vmax is 4.7 x 10(-5) m/s. Endogenous substrates, including the tryptophan precursor indole, the neurotransmitter precursor beta-phenylethylamine, and a variety of peroxidase and laccase substrates, as well as carcinogenic benzidines, were found to be oxidized by catalase or to inhibit this activity. Several dietary plant micronutrients that inhibit carcinogenesis, including indole-3-carbinol, indole-3-carboxaldehyde, ferulic acid, vanillic acid, and epigallocatechin-3-gallate, were effective inhibitors of the activity of catalase oxidase. Difference spectroscopy revealed that catalase oxidase/substrate interactions involve the heme-iron; the resulting spectra show time-dependent decreases in the ferric heme of the enzyme with corresponding increases in the formation of an oxyferryl intermediate, potentially reflecting a compound II-like intermediate. These data suggest a mechanism of oxidase activity involving the formation of an oxygen-bound, substrate-facilitated reductive intermediate. Our results describe a novel function for catalase potentially important in metabolism of endogenous substrates and in the action of carcinogens and chemopreventative agents.

Purification of lactoperoxidase from creek-water buffalo milk and investigation of kinetic and antibacterial properties

Water buffalo lactoperoxidase (WBLP) was purified with Amberlite CG 50 H+ resin, CM Sephadex C-50 ion-exchange chromatography, and Sephadex G-100 gel filtration chromatography from skim milk. All purification steps of the WBLP were shown with SDS-PAGE and Rz (A412/A280) controlled the purification degree of the enzyme. Rz value for the purified WBLP was 0.8. To determine purification steps and kinetic properties, the activity of enzyme was measured by using 2,2-azino-bis-(3-ethylbenzthiazoline-6 sulfonic acid) diammonium salt (ABTS) as a choromogenic substrate at pH=6. Km, Vmax, optimum pH, and optimum temperature for the WBLP were found by means of graphics for ABTS as substrates. Optimum pH and optimum temperature of the WBLP were 6 and 60 degrees C, respectively. Km value at optimum pH and optimum temperature for the WBLP was 0.82 mM. Vmax value at optimum pH and optimum temperature was 13.7 micromol/mL x min. Km value at optimum pH and 25 degrees C for the WBLP was 0.77 mM. Vmax value at optimum pH and 25 degrees C was 4.83 micromol/mL x min. The purified WBLP was found to have high antibacterial activity in a thiocynate-H2O2 medium for some pathogenic bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginose, Shigella sonnei, Staphylococcus saphrophyticus, Staphylococcus epidermidis, and Shigella dysenteriae and compared with well known antibacterial substances such as tetracycline, penicillin, and netilmicine.