Cytotoxic properties of salivary oxidants

1990 ◽  
Vol 258 (1) ◽  
pp. C115-C121 ◽  
Author(s):  
M. B. Grisham ◽  
E. M. Ryan
Keyword(s):  
Membrane Permeability ◽  
Low Ph ◽  
Extracellular Ph ◽  
Human Erythrocytes ◽  
Acidic Ph ◽  
Cytotoxic Potential ◽  
Oxidize Glutathione ◽  
Ph Values ◽  
Ph Dependent ◽  
Conjugate Base

Salivary peroxidase and to a lesser extent myeloperoxidase are present in significant concentrations in saliva and catalyze the oxidation of thiocyanate anion (SCN-) by H2O2 to yield the potent oxidants hypothiocyanous acid (HOSCN) and its conjugate base hypothiocyanite anion (OSCN-). The objective of this study was to characterize the cytotoxic potential of peroxidase-generated HOSCN/OSCN- toward human erythrocytes. We found that HOSCN/OSCN- (0.25 mM) generated by the peroxidase-H2O2-SCN- system caused significant hemolysis at pH 6.0 but not at pH 6.5, 7.0, or 7.4. Erythrocyte hemoglobin (OxyHb) was oxidized to methemoglobin (MetHb) at all pH values tested; however, the rate of MetHb formation was dramatically increased at low pH and was not affected by inosine hexaphosphate, suggesting that hemoglobin was oxidized primarily by HOSCN. Concurrent with oxidation of hemoglobin (Hb), there was a pH-dependent consumption of HOSCN/OSCN- with more of the oxidant consumed at pH 6.0 compared with pH 6.5, 7.0, or 7.4. The enhanced oxidation of Hb at acidic pH was not due simply to increased membrane permeability by the uncharged species (HOSCN), since both erythrocyte lysate Hb and purified Hb were oxidized to the same extent at low pH as were intact erythrocytes. It is concluded that both OSCN- and HOSCN enter human erythrocytes where the protonated oxidant (HOSCN) mediates hemolysis and oxidizes OxyHb to MetHb, whereas both HOSCN and OSCN- oxidize glutathione (GSH). These data suggest that the extracellular pH may play an important role in modulating the cytotoxic properties of salivary oxidants.

scholarly journals PHR2 of Candida albicans encodes a functional homolog of the pH-regulated gene PHR1 with an inverted pattern of pH-dependent expression.

1997 ◽  
Vol 17 (10) ◽  
pp. 5960-5967 ◽  
Author(s):  
F A Mühlschlegel ◽  
W A Fonzi
Keyword(s):  
Candida Albicans ◽  
Mutant Strain ◽  
Low Ph ◽  
Predicted Amino Acid Sequence ◽  
Acidic Ph ◽  
Null Mutant ◽  
Alkaline Ph ◽  
Ph Values ◽  
Functional Homolog ◽  
Morphological Defects

Deletion of PHR1, a pH-regulated gene of Candida albicans, results in pH-conditional defects in growth, morphogenesis, and virulence evident at neutral to alkaline pH but absent at acidic pH. Consequently, we searched for a functional homolog of PHR1 active at low pH. This resulted in the isolation of a second pH-regulated gene, designated PHR2. The expression of PHR2 was inversely related to that of PHR1, being repressed at pH values above 6 and progressively induced at more acidic pH values. The predicted amino acid sequence of the PHR2 protein, Phr2p, was 54% identical to that of Phr1p. A PHR2 null mutant exhibited pH-conditional defects in growth and morphogenesis analogous to those of PHR1 mutants but manifest at acid rather than alkaline pH values. Engineered expression of PHR1 at acid pH in a PHR2 mutant strain and PHR2 at alkaline pH in a PHR1 mutant strain complemented the defects in the opposing mutant. Deletion of both PHR1 and PHR2 resulted in a strain with pH-independent, constitutive growth and morphological defects. These results indicate that PHR1 and PHR2 represent a novel pH-balanced system of functional homologs required for C. albicans to adapt to environments of diverse pH.

scholarly journals pH-dependent interconversion of two forms of tyrosinase in human skin

1988 ◽  
Vol 252 (2) ◽  
pp. 481-487 ◽  
Author(s):  
R K Tripathi ◽  
C Chaya Devi ◽  
A Ramaiah
Keyword(s):  
Human Skin ◽  
Sodium Phosphate ◽  
Inhibitory Concentration ◽  
Low Ph ◽  
The Other ◽  
Gradual Change ◽  
Ph Values ◽  
Sodium Phosphate Buffer ◽  
Solubilized Enzyme ◽  
Ph Dependent

1. We have shown that the characteristic lag in cresolase activity of human skin tyrosinase at inhibitory concentration of tyrosine was absent at all pH values studied, i.e. pH 5.2, 5.7, 6.2 and 6.8, if the enzyme solubilized at low pH was used as the source of enzyme, but the same enzyme when dialysed against buffers of various pH values showed linear activity only at pH 5.2 and was not inhibited by excess tyrosine, whereas at higher pH values it exhibited a lag and inhibition by excess tyrosine. 2. However, the enzyme solubilized in buffer/detergent, pH 6.8, when dialysed against buffer of the same pH showed linear activity at pH 5.2 and non-linear activity at pH 6.8. 3. The water/detergent-solubilized enzyme from human skin melanosomes showed linear activity even at inhibitory concentrations of tyrosine at pH 5.2 and 6.8 up to 2 h, but acceleration of rate was observed after 2 h for the enzyme measured at pH 6.8. 4. After dialysis of the water/detergent-solubilized enzyme against double-glass-distilled water, it still exhibits linear activity at inhibitory concentration of tyrosines at pH 6.8 for the first 2 h, but the same enzyme when dialysed against 0.02 M-sodium phosphate buffer, pH 6.8, exhibits negligible activity up to 1/2 h, in contrast with considerable activity before dialysis during the same interval of time, but without any loss of activity at later intervals of incubation time. 5. On the basis of these results, it is concluded that the enzyme exists in at least two interconvertible forms, one without lag and inhibition by excess tyrosine and the other with lag and inhibition by excess tyrosine. These two forms are interconvertible only by gradual change in pH over a period of hours.

scholarly journals Enzootic Nasal Tumor Virus Envelope Requires a Very Acidic pH for Fusion Activation and Infection

2008 ◽  
Vol 82 (18) ◽  
pp. 9023-9034 ◽  
Author(s):  
Marceline Côté ◽  
Thomas J. Kucharski ◽  
Shan-Lu Liu
Keyword(s):  
Low Ph ◽  
Prolonged Treatment ◽  
Close Relative ◽  
Target Cells ◽  
Acidic Ph ◽  
Enzootic Nasal Tumor Virus ◽  
Tumor Virus ◽  
Nasal Tumor ◽  
Ph Dependent ◽  
Env Protein

ABSTRACT Enzootic nasal tumor virus (ENTV) is a close relative of jaagsiekte sheep retrovirus (JSRV), and the two viruses use the same receptor, hyaluronidase 2 (Hyal2), for cell entry. We report here that, unlike the JSRV envelope (Env) protein, the ENTV Env protein does not induce cell fusion at pHs of 5.0 and above but requires a much lower pH (4.0 to 4.5) for fusion to occur. The entry of ENTV Env pseudovirions was substantially inhibited by bafilomycin A1 (BafA1) but was surprisingly enhanced by lysosomotropic agents and lysosomal protease inhibitors following a 4- to 6-h treatment period; of note, prolonged treatment with BafA1 or ammonium chloride completely blocked ENTV entry. Unlike typical pH-dependent viruses, ENTV Env pseudovirions were virtually resistant to inactivation at a low pH (4.5 or 5.0). Using chimeras formed from ENTV and JSRV Env proteins, we demonstrated that the transmembrane (TM) subunit of ENTV Env is primarily responsible for its unusually low pH requirement for fusion but found that the surface (SU) subunit of ENTV Env also critically influences its relatively low and pH-dependent fusion activity. Furthermore, the poor infectivity of ENTV pseudovirions in human cells was significantly improved by either replacing the SU subunit of ENTV Env with that of JSRV Env or overexpressing the functional Hyal2 receptor in target cells, suggesting that ENTV SU-Hyal2 interaction is likely to be the limiting step for viral infectivity. Collectively, our data reveal that the fusogenicity of ENTV Env is intrinsically lower than that of JSRV Env and that ENTV requires a more acidic pH for fusion, which may occur in an intracellular compartment(s) distinct from that used by JSRV.

scholarly journals Oligomerization ofSulfolobus solfataricussignature amidase is promoted by acidic pH and high temperature

Archaea ◽  
2005 ◽  
Vol 1 (6) ◽  
pp. 411-423 ◽  
Author(s):  
Anna Scotto D’Abusco ◽  
Rita Casadio ◽  
Gianluca Tasco ◽  
Laura Giangiacomo ◽  
Anna Giartosio ◽  
...  
Keyword(s):  
Analytical Ultracentrifugation ◽  
Ph Dependence ◽  
Sulfolobus Solfataricus ◽  
Gel Permeation Chromatography ◽  
Acidic Ph ◽  
Polar Solvents ◽  
Ph Values ◽  
Gel Permeation ◽  
Ph Dependent ◽  
Decreasing Ph

The recombinant amidase from the hyperthermophylic archaeonSulfolobus solfataricus(SSAM) a signature amidase, was cloned, purified and characterized. The enzyme is active on a large number of aliphatic and aromatic amides over the temperature range 60–95 °C and at pH values between 4.0 and 9.5, with an optimum at pH 5.0. The recombinant enzyme is in the form of a dimer of about 110 kD that reversibly associates into an octamer in a pH-dependent reaction. The pH dependence of the state of association was studied using gel permeation chromatography, analytical ultracentrifugation and dynamic light scattering techniques.pH 7.0 all three techniques show the presence of two species, in about equal amounts, which is compatible with the existence of a dimeric and an octameric form. In decreasing pH, the dimers formed the octameric species and in increasing pH, the octameric species was converted to dimers. Above pH 8.0, only dimers were present, below pH 3.0 only octamers were present. The association of dimers into octamers decreased in non-polar solvents and increased with temperature. A mutant (Y41C) was obtained that did not show this behavior.

scholarly journals PE2 Cleavage Mutants of Sindbis Virus: Correlation between Viral Infectivity and pH-Dependent Membrane Fusion Activation of the Spike Heterodimer

2001 ◽  
Vol 75 (22) ◽  
pp. 11196-11204 ◽  
Author(s):  
Jolanda M. Smit ◽  
William B. Klimstra ◽  
Kate D. Ryman ◽  
Robert Bittman ◽  
Robert E. Johnston ◽  
...  
Keyword(s):  
Infected Cell ◽  
Membrane Fusion ◽  
Sindbis Virus ◽  
Rna Replication ◽  
Low Ph ◽  
Receptor Interaction ◽  
Viral Infectivity ◽  
Acidic Ph ◽  
Virus Receptor ◽  
Ph Dependent

ABSTRACT The spike glycoprotein E2 of Sindbis virus (SIN) is synthesized in the infected cell as a PE2 precursor protein, which matures through cleavage by a cellular furin-like protease. Previous work has shown that SIN mutants impaired in PE2 cleavage are noninfectious on BHK-21 cells, the block in infection being localized at a step after virus-receptor interaction but prior to RNA replication. Here, we studied the membrane fusion properties of SIN PE2 cleavage mutants and observed that these viruses are impaired in their ability to form an E1 homotrimer and to fuse with liposomes at a mildly acidic pH. The block in spike rearrangement and fusion could be overridden by exposure of the mutant viruses to very low pH (<4.5). Cleavage mutants with second-site resuscitating mutations in PE2 were highly infectious for BHK-21 cells. The ability of these viruses to form E1 homotrimers and to fuse at a mildly acidic pH was completely restored despite a sustained lack of PE2 cleavage.

scholarly journals Inosine/pyruvate/phosphate medium but not adenosine/pyruvate/phosphate medium introduces millimolar amounts of 5-phosphoribosyl 1-pyrophosphate in human erythrocytes. A 31P-n.m.r. study

1990 ◽  
Vol 266 (2) ◽  
pp. 441-446 ◽  
Author(s):  
A Petersen ◽  
B Quistorff
Keyword(s):  
Human Erythrocyte ◽  
Inorganic Phosphate ◽  
Fold Increase ◽  
Extracellular Ph ◽  
Human Erythrocytes ◽  
Intracellular Concentration ◽  
Maximum Value ◽  
Ph Dependent ◽  
High Concentrations ◽  
Phosphate Medium

Incubation of human erythrocytes in medium containing inosine (10 mM), pyruvate (10 mM), phosphate (50 mM) and NaCl (75 mM) at pH 6.6 leads to a more than 1000-fold increase in the concentration of 5-phosphoribosyl 1-pyrophosphate (PRPP), as identified and quantified by 31P-n.m.r. spectroscopy. The accumulation is highly pH-dependent, with a maximum at extracellular pH 6.60, and the maximum value of 1.3-1.6 mmol/l of erythrocytes is attained within 1 h at 37 degrees C. PRPP was accumulated despite high concentrations of 2,3-bisphosphoglycerate (2,3-BPG), an inhibitor of PRPP synthetase. The concentration of PRPP correlated with the intracellular concentration of inorganic phosphate (Pi). Substitution of either adenosine or adenosine plus inosine for inosine in the medium did not lead to 31P-n.m.r.-detectable accumulation of PRPP. These results show that neither 2,3-BPG nor PRPP itself inhibits the synthesis of PRPP in the human erythrocyte. Adenosine, however, prevents the inosine-stimulated accumulation of PRPP.

scholarly journals Low-pH-Induced Membrane Fusion Mediated by Human Metapneumovirus F Protein Is a Rare, Strain-Dependent Phenomenon

2008 ◽  
Vol 82 (17) ◽  
pp. 8891-8895 ◽  
Author(s):  
Sander Herfst ◽  
Vicente Mas ◽  
Lorena S. Ver ◽  
Rutger J. Wierda ◽  
Albert D. M. E. Osterhaus ◽  
...  
Keyword(s):  
Membrane Fusion ◽  
Low Ph ◽  
Human Metapneumovirus ◽  
Acidic Ph ◽  
Induced Membrane ◽  
F Protein ◽  
Genetic Lineages ◽  
Ph Dependent ◽  
Strain Dependent

ABSTRACT Membrane fusion promoted by human metapneumovirus (HMPV) fusion (F) protein was suggested to require low pH (R. M. Schowalter, S. E. Smith, and R. E. Dutch, J. Virol. 80:10931-10941, 2006). Using prototype F proteins representing the four HMPV genetic lineages, we detected low-pH-dependent fusion only with some lineage A proteins and not with lineage B proteins. A glycine at position 294 was found responsible for the low-pH requirement in lineage A proteins. Only 6% of all HMPV lineage A F sequences have 294G, and none of the lineage B sequences have 294G. Thus, acidic pH is not a general trigger of HMPV F proteins for activity.

Antibacterial Protection by Enterocin AS-48 in Sport and Energy Drinks with Less Acidic pH Values

2009 ◽  
Vol 72 (4) ◽  
pp. 881-884 ◽  
Author(s):  
PILAR MARTINEZ VIEDMA ◽  
HIKMATE ABRIOUEL ◽  
NABIL BEN OMAR ◽  
ROSARIO LUCAS LÓPEZ ◽  
EVA VALDIVIA ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Pathogenic Bacteria ◽  
Dental Health ◽  
Energy Drinks ◽  
Low Ph ◽  
Final Concentration ◽  
Acidic Ph ◽  
Time Increase ◽  
Natural Preservative ◽  
Ph Values

The low pH and acid content found in sports and energy drinks are a matter of concern in dental health. Raising the pH may solve this problem, but at the same time increase the risks of spoilage or presence of pathogenic bacteria. In the present study, commercial energy drinks were adjusted to pH 5.0 and challenged with Listeria monocytogenes (drinks A to F), Staphylococcus aureus, Bacillus cereus, and Bacillus licheniformis (drink A) during storage at 37°C. L. monocytogenes was able to grow in drink A and survived in drinks D and F for at least 2 days. Addition of enterocin AS-48 (1 μg/ml final concentration) rapidly inactivated L. monocytogenes in all drinks tested. S. aureus and B. cereus also survived quite well in drink A, and were completely inactivated by 12.5 μg/ml enterocin AS-48 after 2 days of storage or by 25 μg/ml bacteriocin after 1 day. B. licheniformis was able to multiply in drink A, but it was completely inactivated by 5 μg/ml enterocin AS-48 after 2 days of storage or by 12.5 μg/ml bacteriocin after 1 day. Results from the present study suggest that enterocin AS-48 could be used as a natural preservative against these target bacteria in less acidic sport and energy drinks.

scholarly journals Bleomycin-detectable iron in knee-joint synovial fluid from arthritic patients and its relationship to the extracellular antioxidant activities of caeruloplasmin, transferrin and lactoferrin

1987 ◽  
Vol 245 (2) ◽  
pp. 415-421 ◽  
Author(s):  
J M C Gutteridge
Keyword(s):  
Knee Joint ◽  
Antioxidant Activities ◽  
Lipid Peroxide ◽  
Oxygen Radical ◽  
Low Ph ◽  
Acidic Ph ◽  
Peroxide Content ◽  
Ph Values ◽  
Synovial Fluids ◽  
Radical Damage

Some 40% of knee-joint synovial fluids from arthritic patients show the presence of bleomycin-detectable iron. This is released from a protein component of the fluid to bleomycin at acidic pH values. Patients whose fluids release iron have lower contents of transferrin, lactoferrin and caeruloplasmin than do patients whose fluids do not release iron to bleomycin. These proteins are important extracellular antioxidants, and measured antioxidant activities are extremely low in the iron-releasing fluids. The propensity of some fluids to release iron at low pH values, characteristic of the microenvironment beneath adherent macrophages, coupled with their decreased antioxidant protection against iron-stimulated oxygen-radical damage, might explain previously reported correlations between clinical disease severity, lipid peroxide content and the presence of bleomycin-detectable iron [Rowley, Gutteridge, Blake, Farr & Halliwell (1984) Clin. Sci. 66, 691-695].

Influence of pH on Cadmium Removal by Mineral Adsorbent

2012 ◽  
Vol 518-523 ◽  
pp. 3026-3029
Author(s):  
Chun Fang Tang ◽  
Ke Lin Li ◽  
Cheng Feng Li
Keyword(s):  
Low Ph ◽  
Langmuir Equation ◽  
Maximum Amount ◽  
Cadmium Removal ◽  
Ph Values ◽  
Adsorption Data ◽  
Dependent Model ◽  
Adsorption Amount ◽  
Ph Dependent ◽  
Influence Of Ph

The effect of pH on Cd adsorption was studied using red soil as an adsorbent in this study.The curve of Cd adsorbed vs pH showed that the adsorption amount increased slowly at low pH, then quickly with the increase of pH, and reached the maximum amount at high pH. The adsorption data at different pH values and initial Cd(II) concentrations were fitted well by Langmuir isotherm. At last, a pH-dependent model of adsorption isotherms of Cd was established by substituting the fitting results obtained from experimental data for the parameters in Langmuir equation.

Sign in / Sign up

Export Citation Format

Share Document