Inhibition effects of selected thiophene-2-sulfonamides on lactoperoxidase.

Lactoperoxidase (LPO, E.C.1.11.1.7) is a natural antibacterial agent which is secreted from salivary, mammary, and other mucosal glands. It is one of the crucial enzymes in biological systems, so protection of LPO activity is extremely important for the immune system. Within the scope of this study; in vitro effects of some thiophene-2-sulfonamide derivatives (1a-7a) on bovine milk LPO enzymatic activity were investigated. LPO was purified from the Sepharose-4B-L-tyrosine-5-amino-2-methylbenzenesulfonamide column prepared using affinity chromatography technique with a yield of 169.66 EU/mg specific activity in 452.44 times. As a result, 5-(2-thienylthio) thiophene-2-sulfonamide demonstrated the strongest inhibition impact among these compounds. This molecule has shown a competitive inhibition and it was determined that the IC50 value was 3.4 nM and the Ki value was 2 ± 0.6 nM.

Lactoperoxidase, an antimicrobial enzyme, is inhibited by some indazoles.

Lactoperoxidase (LPO) has bactericidal and bacteriostatic activity on various microorganisms and it creates a natural antimicrobial defense system. So, LPO is one of the essential enzyme in biological systems and the protection of the LPO activity is extremely important for the immune system. Because of these features, the protection of the activity of the LPO has vital importance for the health of the organisms. Also, LPO is used in various sectors from cosmetics industry to agriculture industry due to its broad antimicrobial properties. Therefore, the identification of inhibitors and activators of the LPO is becoming increasingly important. In present study we aimed to investigate the inhibitory effects of some indazoles [1H-indazole (1a), 4-Bromo-1H-indazole (2a), 6-Bromo-1H-indazole (3a), 7-Bromo-1H-indazole (4a), 4-chloro-1H-indazole (5a), 6-chloro-1H-indazole (6a), 7-chloro-1H-indazole (7a), 4-fluoro-1H-indazole (8a), 6-fluoro-1H-indazole (9a), 7-fluoro-1H-indazole (10a)] on bovine milk LPO. Indazole derivatives are heterocyclic organic molecules with a wide range of biological activity. For this aim, bovine milk LPO was purified using Sepharose-4B-l-tyrosine-5-amino-2-methyl benzenesulfonamide affinity chromatography method. Then, the potential inhibitory effects of indazoles on LPO activity were investigated. Ki values were calculated for each indazole molecule. Ki values were ranging from 4.10 to 252.78 µM for 1a to10a. All of the indazole molecules we studied showed strong inhibitory effect on LPO activity. Also we determined inhibition types of the indazoles to clarify the mechanisms of inhibition.

The inhibition of lactoperoxidase catalytic activity through mesna (2-mercaptoethane sodium sulfonate).

Here, we show that mesna (sodium-2-mercaptoethane sulfonate), primarily used to prevent nephrotoxicity and urinary tract toxicity caused by chemotherapeutic agents such as cyclophosphamide and ifosfamide, modulates the catalytic activity of lactoperoxidase (LPO) by binding tightly to the enzyme, functioning either as a one electron substrate for LPO Compounds I and II, destabilizing Compound III. Lactoperoxidase is a hemoprotein that utilizes hydrogen peroxide (H2O2) and thiocyanate (SCN-) to produce hypothiocyanous acid (HOSCN), an antimicrobial agent also thought to be associated with carcinogenesis. Our results revealed that mesna binds stably to LPO within the SCN- binding site, dependent of the heme iron moiety, and its combination with LPO-Fe(III) is associated with a disturbance in the water molecule network in the heme cavity. At low concentrations, mesna accelerated the formation and decay of LPO compound II via its ability to serve as a one electron substrate for LPO compounds I and II. At higher concentrations, mesna also accelerated the formation of Compound II but it decays to LPO-Fe(III) directly or through the formation of an intermediate, Compound I*, that displays characteristic spectrum similar to that of LPO Compound I. Mesna inhibits LPO's halogenation activity (IC50 value of 9.08 µM) by switching the reaction from a 2e- to a 1e- pathway, allowing the enzyme to function with significant peroxidase activity (conversion of H2O2 to H2O without generation of HOSCN). Collectively, mesna interaction with LPO may serve as a potential mechanism for modulating its steady-state catalysis, impacting the regulation of local inflammatory and infectious events.

Structural studies on inhibitory mechanisms of antibiotic, corticosteroid and catecholamine molecules on lactoperoxidase.

AIM: Lactoperoxidase (LPO) is an essential protein with broad spectrum antimicrobial activity present in mammalian milk. It imparts immunity to infants against wide range of pathogenic infections. Several in vitro studies have shown inhibition of LPO activity by pharmaceutical compounds including commonly used antibiotics such as ampicillin and gentamicin, and molecules like prednisolone, norepinephrine, etc. Prescription of such drugs to lactating mothers might have adverse health effects on infants. The aim of our study was the elucidation of the structural aspects of the inhibitory mechanism of ampicillin, gentamicin, amoxicillin, prednisolone and norepinephrine on LPO. MATERIAL AND METHODS: Three dimensional structure of camel LPO (cLPO) was developed using homology modeling and used for in silico experimental studies. The Schrödinger induced fit docking along with binding affinity estimation experiments were performed. The cLPO and Ligands were prepared using Protein Preparation Wizard and Ligprep modules available in Schrodinger suite. For estimating Binding affinity Prime Molecular Mechanics with Generalized Born and Surface Area (MMGB-SA) module was used. KEY RESULTS: The five drug ligands formed three to five hydrogen bonding interactions with cLPO. Amino acids Arg-231, Asp-232, Ser-370, Arg-371 and Glu-374 of cLPO were crucial for these interactions. The binding affinity values for gentamicin were highest and for norepinephrine were the lowest. SIGNIFICANCE: This study concludes that the five drug molecules show potential ability to inhibit the LPO activity. Further, a very high sequence similarity of cLPO with human LPO imparts high significance to these conclusions in relation to human health especially in new born infants.

Interference of carbidopa and other catechols with reactions catalyzed by peroxidases.

BACKGROUND: A number of compounds, including ascorbic acid, catecholamines, flavonoids, p-diphenols and hydrazine derivatives have been reported to interfere with peroxidase-based medical diagnostic tests (Trinder reaction) but the mechanisms of these effects have not been fully elucidated. METHODS: Reactions of bovine myeloperoxidase with o-dianisidine, bovine lactoperoxidase with ABTS and horseradish peroxidase with 4-aminoantipyrine/phenol in the presence of carbidopa, an anti-Parkinsonian drug, and other catechols, including l-dopa, were monitored spectrophotometrically and by measuring hydrogen peroxide consumption. RESULTS: Chromophore formation in all three enzyme/substrate systems was blocked in the presence of carbidopa and other catechols. However, the rates of hydrogen peroxide consumption were not much affected. Irreversible enzyme inhibition was also insignificant. CONCLUSIONS: Tested compounds reduced the oxidation products or intermediates of model substrates thus preventing chromophore formation. This interference may affect interpretation of results of diagnostic tests in samples from patients with Parkinson's disease treated with carbidopa and l-dopa. GENERAL SIGNIFICANCE: This mechanism allows prediction of interference in peroxidase-based diagnostic tests for other compounds, including drugs and natural products.

Discovery of Novel Potent Reversible and Irreversible Myeloperoxidase Inhibitors Using Virtual Screening Procedure.

The heme enzyme myeloperoxidase (MPO) participates in innate immune defense mechanism through formation of microbicidal reactive oxidants. However, evidence has emerged that MPO-derived oxidants contribute to propagation of inflammatory diseases. Because of the deleterious effects of circulating MPO, there is a great interest in the development of new efficient and specific inhibitors. Here, we have performed a novel virtual screening procedure, depending on ligand-based pharmacophore modeling followed by structure-based virtual screening. Starting from a set of 727842 compounds, 28 molecules were selected by this virtual method and tested on MPO in vitro. Twelve out of 28 compounds were found to have an IC50 less than 5 µM. The best inhibitors were 2-(7-methoxy-4-methylquinazolin-2-yl)guanidine (28) and (R)-2-(1-((2,3-dihydro-1H-imidazol-2-yl)methyl)pyrrolidin-3-yl)-5-fluoro-1H-benzo[d]imidazole (42) with IC50 values of 44 and 50 nM, respectively. Studies on the mechanism of inhibition suggest that 28 is the first potent mechanism-based inhibitor and inhibits irreversibly MPO at nanomolar concentration.

The inhibition effects of some natural products on lactoperoxidase purified from bovine milk.

In this study, inhibition profiles of some natural products, which are digoxin, L-Dopa, dopamine, isoliquiritigenin, and 1,1,2,2-tetrakis(p-hydroxyphenyl)ethane (Tetrakis), were investigated against bovine lactoperoxidase (LPO) enzyme. Digoxin, L-Dopa, and dopamine are active ingredients of some drugs, which have important functions in our body, especially in cases of heart failure. Isoliquiritigenin and tetrakis are types of natural phenolic compounds, which play an important role in cancer prevention and treatment. LPO enzyme was purified from bovine milk using sepharose-4B-l-tyrosine sulfonamide affinity column chromatography. LPO is responsible for the nonimmune biological defense system and has antibacterial activity so selection of these active substances is important. The inhibition studies are performed with the ABTS substrate. Bovine LPO enzyme was effectively inhibited by phenolic molecules. Ki values of these natural products were found as 0.20 ± 0.09, 0.22 ± 0.17, 0.49 ± 0.11, 0.49 ± 0.27, and 1.20 ± 0.25 µM, respectively. Tetrakis and digoxin exhibited noncompetitive inhibition, and other molecules showed competitive inhibition.

Secondary Sulfonamides as Effective Lactoperoxidase Inhibitors.

Secondary sulfonamides (4a-8h) incorporating acetoxybenzamide, triacetoxybenzamide, hydroxybenzamide, and trihydroxybenzamide and possessing thiazole, pyrimidine, pyridine, isoxazole and thiadiazole groups were synthesized. Lactoperoxidase (LPO, E.C.1.11.1.7), as a natural antibacterial agent, is a peroxidase enzyme secreted from salivary, mammary, and other mucosal glands. In the present study, the in vitro inhibitory effects of some secondary sulfonamide derivatives (4a-8h) were examined against LPO. The obtained results reveal that secondary sulfonamide derivatives (4a-8h) are effective LPO inhibitors. The Ki values of secondary sulfonamide derivatives (4a-8h) were found in the range of 1.096 × 10-3 to 1203.83 µM against LPO. However, the most effective inhibition was found for N-(sulfathiazole)-3,4,5-triacetoxybenzamide (6a), with Ki values of 1.096 × 10-3 ± 0.471 × 10-3 µM as non-competitive inhibition.

Improved chromatographic method for purification of lactoperoxidase from different milk sources.

Our previous studies showed that sulfanilamide is a new competitive inhibitor of and can be used in the purification of lactoperoxidase (LPO, EC1.11.1.7) from milk. However, this method has some disadvantages like a lower purification factor. The aim of the present study is to improve the purification process of milk LPO from different sources. For this purpose, 16 commercial sulfanilamide derivatives were selected for inhibition studies to determine the best inhibitor of bovine LPO by calculating kinetic parameters. A cyanogen bromide-activated Sepharose 4B affinity matrix was synthesized by coupling with each competitive inhibitor. Among the inhibitors, 5-amino-2-methylbenzenesulfonamide and 2-chloro-4-sulfamoylaniline were used as ligands for the purification of LPO from bovine, buffalo, cow, and goat milks with 1059.37, 509.09, 232.55, and 161.90, and 453.12-, 151.86-, 869.00-, and 447.57-fold, respectively. Our results show that 5-amino-2-methylbenzenesulfonamide, 2-chloro-4-sulfamoylaniline, and 5-amino-1-naphthalenesulfonamide are the best inhibitors for one-step purification of the enzyme.

Gut Microbiota Conversion of Dietary Ellagic Acid into Bioactive Phytoceutical Urolithin A Inhibits Heme Peroxidases.

Numerous studies signify that diets rich in phytochemicals offer many beneficial functions specifically during pathologic conditions, yet their effects are often not uniform due to inter-individual variation. The host indigenous gut microbiota and their modifications of dietary phytochemicals have emerged as factors that greatly influence the efficacy of phytoceutical-based intervention. Here, we investigated the biological activities of one such active microbial metabolite, Urolithin A (UA or 3,8-dihydroxybenzo[c]chromen-6-one), which is derived from the ellagic acid (EA). Our study demonstrates that UA potently inhibits heme peroxidases i.e. myeloperoxidase (MPO) and lactoperoxidase (LPO) when compared to the parent compound EA. In addition, chrome azurol S (CAS) assay suggests that EA, but not UA, is capable of binding to Fe3+, due to its catechol-like structure, although its modest heme peroxidase inhibitory activity is abrogated upon Fe3+-binding. Interestingly, UA-mediated MPO and LPO inhibition can be prevented by innate immune protein human NGAL or its murine ortholog lipocalin 2 (Lcn2), implying the complex nature of host innate immunity-microbiota interactions. Spectral analysis indicates that UA inhibits heme peroxidase-catalyzed reaction by reverting the peroxidase back to its inactive native state. In support of these in vitro results, UA significantly reduced phorbol myristate acetate (PMA)-induced superoxide generation in neutrophils, however, EA failed to block the superoxide generation. Treatment with UA significantly reduced PMA-induced mouse ear edema and MPO activity compared to EA treated mice. Collectively, our results demonstrate that microbiota-mediated conversion of EA to UA is advantageous to both host and microbiota i.e. UA-mediated inhibition of pro-oxidant enzymes reduce tissue inflammation, mitigate non-specific killing of gut bacteria, and abrogate iron-binding property of EA, thus providing a competitive edge to the microbiota in acquiring limiting nutrient iron and thrive in the gut.

Potent Inhibitory Effects of Some Phenolic Acids on Lactoperoxidase.

Lactoperoxidase (LPO) plays a key role in immune response against pathogens. In this study, we examined the effects of some phenolic acids on LPO. For this purpose, bovine milk LPO was purified 380.85-fold with a specific activity of 26.66 EU/mg and overall yield of 73.33% by using Amberlite CG-50 H+ resin and CNBr-activated Sepharose-4B-l-tyrosine-sulfanilamide affinity chromatography. After purification, the in vitro effects of phenolic acids (tannic acid, 3,4-dihydroxybenzoic acid, 3,5- dihydroxybenzoic acid, chlorogenic acid, sinapic acid, 4-hydroxybenzoic acid, vanillic acid, salicylic acid, and 3-hydroxybenzoic acid) were investigated on LPO. These phenolic acids showed potent inhibitory effect on LPO. Ki values for these phenolic acids were found as 0.0129 nM, 0.132 µM, 0.225 µM, 0.286 µM, 0.333 µM, 2.33 µM, 10.82 µM, 0.076 mM, and 0.405 mM, respectively. Sinapic acid and 4-hydroxybenzoic acid exhibited noncompetitive inhibition; 3,4-dihydroxybenzoic acid showed uncompetitive inhibition, and other phenolic acids showed competitive inhibition.

Rosmarinic acid inhibits some metabolic enzymes including glutathione S-transferase, lactoperoxidase, acetylcholinesterase, butyrylcholinesterase and carbonic anhydrase isoenzymes.

Rosmarinic acid (RA) is a natural polyphenol contained in many aromatic plants with promising biological activities. Carbonic anhydrases (CAs, EC 4.2.1.1) are widespread and intensively studied metalloenzymes present in higher vertebrates. Acetylcholinesterase (AChE, E.C. 3.1.1.7) is intimately associated with the normal neurotransmission by catalysing the hydrolysis of acetylcholine to acetate and choline and acts in combination with butyrylcholinesterase (BChE) to remove acetylcholine from the synaptic cleft. Lactoperoxidase (LPO) is an enzyme involved in fighting pathogenic microorganisms, whereas glutathione S-transferases (GSTs) are dimeric proteins present both in prokaryotic and in eukaryotic organisms and involved in cellular detoxification mechanisms. In the present study, the inhibition effects of rosmarinic acid on tumour-associated carbonic anhydrase IX and XII isoenzymes, AChE, BChE, LPO and GST enzymes were evaluated. Rosmarinic acid inhibited these enzymes with Kis in the range between micromolar to picomolar. The best inhibitory effect of rosmarinic acid was observed against both AChE and BChE.

(99m)Tc-amitrole as a novel selective imaging probe for solid tumor: In silico and preclinical pharmacological study.

Lactoperoxidase (LPO) inhibitors are very selective for solid tumor due to their high binding affinity to the LPO enzyme. A computational study was used to select top-ranked LPO inhibitor (alone and in complex with (99m)Tc) with high in silico affinity. The novel prepared (99m)Tc-amitrole complex demonstrated both in silico and in vivo high affinity toward solid tumors.(99m)Tc-amitrole was radio-synthesized with a high radiochemical yield (89.7±3.25). It showed in vitro stability for up to 6h. Its preclinical evaluation in solid tumor-bearing mice showed high retention and biological accumulation in solid tumor cells with a high Target/Non-Target (T/NT) ratio equal to 4.9 at 60min post-injection. The data described previously could recommend (99m)Tc-amitrole as potential targeting scintigraphic probe for solid tumor imaging.

Mode of binding of the antithyroid drug propylthiouracil to mammalian haem peroxidases.

The mammalian haem peroxidase superfamily consists of myeloperoxidase (MPO), lactoperoxidase (LPO), eosinophil peroxidase (EPO) and thyroid peroxidase (TPO). These enzymes catalyze a number of oxidative reactions of inorganic substrates such as Cl(-), Br(-), I(-) and SCN(-) as well as of various organic aromatic compounds. To date, only structures of MPO and LPO are known. The substrate-binding sites in these enzymes are located on the distal haem side. Propylthiouracil (PTU) is a potent antithyroid drug that acts by inhibiting the function of TPO. It has also been shown to inhibit the action of LPO. However, its mode of binding to mammalian haem peroxidases is not yet known. In order to determine the mode of its binding to peroxidases, the structure of the complex of LPO with PTU has been determined. It showed that PTU binds to LPO in the substrate-binding site on the distal haem side. The IC50 values for the inhibition of LPO and TPO by PTU are 47 and 30 µM, respectively. A comparision of the residues surrounding the substrate-binding site on the distal haem side in LPO with those in TPO showed that all of the residues were identical except for Ala114 (LPO numbering scheme), which is replaced by Thr205 (TPO numbering scheme) in TPO. A threonine residue in place of alanine in the substrate-binding site may affect the affinity of PTU for peroxidases.

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.

Interactions between hyaluronic acid, lysozyme, and the glucose oxidase-mediated lactoperoxidase system in enzymatic and candidacidal activities.

OBJECTIVE: To investigate interactions between hyaluronic acid (HA), lysozyme, and the glucose oxidase-mediated lactoperoxidase (GO-LPO) system in enzymatic and candidacidal activities. DESIGN: The influences of HA (0.5, 1.0, and 2.0mg/mL) and lysozyme (30µg/mL hen egg white lysozyme) on the enzymatic activity of GO-LPO system (25µg/mL bovine LPO, 1mM KSCN, 10units/mL GO, and 30µg/mL glucose) were determined by measuring oxidized o-dianisidine production. The influence of the GO-LPO system on lysozyme activity was determined by measuring the turbidity of a Micrococcus lysodeikticus suspension. The effects of interactions between HA, lysozyme, the GO-LPO system on candidacidal activity were examined by pre-incubating various combinations of components. Candidacidal activity was determined by comparing the numbers of colony forming units using Candida albicans ATCC strains 10231, 18804, and 11006. RESULTS: HA inhibited the enzymatic activity of the GO-LPO system in a dose-dependent manner. HA inhibited the candidacidal activities of the GO-LPO system. However, the inhibitory activity of HA was not significantly different according to concentration of HA. The GO-LPO system enhanced the enzymatic activity of lysozyme, though lysozyme did not affect the enzymatic activity of the GO-LPO system. The candidacidal activities of the GO-LPO system and lysozyme were not additive. CONCLUSIONS: HA inhibited the enzymatic and candidacidal activity of the GO-LPO system. The GO-LPO system enhanced the enzymatic activity of lysozyme, but the candidacidal activities were not additive.

Inhibition of lactoperoxidase-catalyzed oxidation by imidazole-based thiones and selones: a mechanistic study.

Herein, we describe the synthesis and biomimetic activity of a series of N,N-disubstituted thiones and selones that contain an imidazole pharmacophore. The N,N-disubstituted thiones do not show any inhibitory activity towards LPO-catalyzed oxidation reactions, but their corresponding N,N-disubstituted selones exhibit inhibitory activity towards LPO-catalyzed oxidation reactions. Substituents on the N atom of the imidazole ring appear to have a significant effect on the inhibition of LPO-catalyzed oxidation and iodination reactions. Selones 16, 17, and 19, which contain methyl, ethyl, and benzyl substituents, exhibit similar inhibition activities towards LPO-catalyzed oxidation reactions with IC50 values of 24.4, 22.5, and 22.5 µM, respectively. However, their activities are almost three-fold lower than that of the commonly used anti-thyroid drug methimazole (MMI). In contrast, selone 21, which contains a N-CH2CH2OH substituent, exhibits high inhibitory activity, with an IC50 value of 7.2 µM, which is similar to that of MMI. The inhibitory activity of these selones towards LPO-catalyzed oxidation/iodination reactions is due to their ability to decrease the concentrations of the co-substrates (H2O2 and I2), either by catalytically reducing H2O2 (anti-oxidant activity) or by forming stable charge-transfer complexes with oxidized iodide species. The inhibition of LPO-catalyzed oxidation/iodination reactions by N,N-disubstituted selones can be reversed by increasing the concentration of H2O2. Interestingly, all of the N,N-disubstituted selones exhibit high anti-oxidant activities and their glutathione peroxidase (GPx)-like activity is 4-12-fold higher than that of the well-known GPx-mimic ebselen. These experimental and theoretical studies suggest that the selones exist as zwitterions, in which the imidazole ring contains a positive charge and the selenium atom carries a large negative charge. Therefore, the selenium moieties of these selones possess highly nucleophilic character. The (77)Se NMR chemical shifts for the selones show large upfield shift, thus confirming the zwitterionic structure in solution.

Production of nitric oxide by human salivary peroxidase and by bovine lactoperoxidase.

Peroxidases catalyze the oxidation of nitrite to nitrate in the presence of hydrogen peroxide. Two pathways may occur: one entailing the intermediate formation of NO(2) and the other implying the generation of peroxynitrite. The products of nitrite (NO(2) (-) ) oxidation by salivary peroxidase (SPO) and commercial bovine lactoperoxidase (LPO) are studied by utilizing an electrochemical assay that allows the direct, continuous monitoring of NO and/or NO(2) and by HPLC to assess nitrates at the end of the reaction. Dialyzed saliva and LPO, in the presence of H(2) O(2) , convert nitrite into nitrate and form some NO, with a molar ratio of 10(3) . In our experimental conditions, no NO(2) was detectable among the products of nitrite oxidation. SCN(-) inhibits NO formation and so does I(-) , although at higher concentrations. No effects are observed with Cl(-) or Br(-) . We conclude that SPO and LPO transform NO(2) (-) into nitrate-forming small amounts of NO in the presence of H(2) O(2) as an intermediate or a by-product, synthesized through the peroxynitrite pathway.

Influences of hyaluronic acid on the anticandidal activities of lysozyme and the peroxidase system.

OBJECTIVE: To investigate the fungistatic and fungicidal activity of hyaluronic acid (HA) and the influences of HA on the anticandidal activities of lysozyme and the peroxidase system. MATERIALS AND METHODS: HA, hen egg-white lysozyme, and the bovine lactoperoxidase system were used. Candida albicans ATCC 10231, 18804, and 11006 strains were used in the experiments. The fungistatic activity of HA was determined by measuring the optical densities of the cultures. The candidacidal activity of HA and the influences of HA on the candidacidal activities of lysozyme and the peroxidase system were determined by comparing the numbers of colony-forming units. RESULTS: Hyaluronic acid displayed inhibitory effects on the growth of C. albicans, and the inhibitory effects were proportional to HA concentration. HA did not have any measurable candidacidal activity. HA showed inhibitory effects on the candidacidal activities of lysozyme, and the peroxidase system that was proportional to HA concentration. HA at 1.0-2.0 mg ml(-1) almost completely inhibited the candidacidal activities of lysozyme and the peroxidase system. CONCLUSIONS: Hyaluronic acid possesses fungistatic activity but no candidacidal activity. HA showed inhibitory effects on the candidacidal activities of lysozyme and the peroxidase system.

Effects of mono- and disaccharides on the antimicrobial activity of bovine lactoperoxidase system.

The effects of mono- and disaccharides on the antimicrobial activity of the lactoperoxidase (LPO) system against Salmonella Enteritidis were investigated. The results clearly reveal that most of the sugars inhibit the antimicrobial activity of the LPO system. The inhibitory potency varies depending on the structure of sugar. L-Fructose and D-allose were strongly inhibitive to the action of the LPO system, while sucrose was the weakest inhibitor. The decreased antimicrobial activity is due to the reduction of LPO catalytic activity by sugar. An inhibitory kinetic study showed the noncompetitive inhibitor. D-Allose and L-fructose yielded strikingly low K(i) values of 0.36 and 0.42 mM, respectively, while the K(i) values of the other sugars ranged from 1.37 to 3.60 mM. Since LPO activity is inhibited by the saccharides, the sugar content in food should be considered when the LPO system is applied to the preservation of food.