Sulfoxides
Transition Elements
Sulfides
Methionine Sulfoxide Reductases
Pseudomonas mendocina
Oxidation-Reduction
Stereoisomerism
Oxidoreductases
Lipoprotein-associated phospholipase A2, platelet-activating factor acetylhydrolase, generates two bioactive products during the oxidation of low-density lipoprotein: use of a novel inhibitor. (1/269)
A novel and potent azetidinone inhibitor of the lipoprotein-associated phospholipase A2 (Lp-PLA2), i.e. platelet-activating factor acetylhydrolase, is described for the first time. This inhibitor, SB-222657 (Ki=40+/-3 nM, kobs/[I]=6. 6x10(5) M-1.s-1), is inactive against paraoxonase, is a poor inhibitor of lecithin:cholesterol acyltransferase and has been used to investigate the role of Lp-PLA2 in the oxidative modification of lipoproteins. Although pretreatment with SB-222657 did not affect the kinetics of low-density lipoprotein (LDL) oxidation by Cu2+ or an azo free-radical generator as determined by assay of lipid hydroperoxides (LOOHs), conjugated dienes and thiobarbituric acid-reacting substances, in both cases it inhibited the elevation in lysophosphatidylcholine content. Moreover, the significantly increased monocyte chemoattractant activity found in a non-esterified fatty acid fraction from LDL oxidized by Cu2+ was also prevented by pretreatment with SB-222657, with an IC50 value of 5.0+/-0.4 nM. The less potent diastereoisomer of SB-222657, SB-223777 (Ki=6.3+/-0.5 microM, kobs/[I]=1.6x10(4) M-1.s-1), was found to be significantly less active in both assays. Thus, in addition to generating lysophosphatidylcholine, a known biologically active lipid, these results demonstrate that Lp-PLA2 is capable of generating oxidized non-esterified fatty acid moieties that are also bioactive. These findings are consistent with our proposal that Lp-PLA2 has a predominantly pro-inflammatory role in atherogenesis. Finally, similar studies have demonstrated that a different situation exists during the oxidation of high-density lipoprotein, with enzyme(s) other than Lp-PLA2 apparently being responsible for generating lysophosphatidylcholine. (+info)An endonuclease from mouse cells specific for single-stranded DNA. (2/269)
An endonuclease with a molecular weight of about 70000 (5-6S) was extensively purified from mouse ascites cells. The enzyme specifically attacks single-stranded DNA which is degraded mainly to oligonucleotides, with 5-10 residues. Supercoiled covalently closed circular phage DNA is converted to the linear relaxed form. The enzyme activity is highly sensitive to salt and can be stimulated by reagents lowering the dielectric constant of the buffer such as dimethylsulfoxide and glycerol. (+info)An organosulfur compound isolated from oil-macerated garlic extract, and its antimicrobial effect. (3/269)
An organosulfur compound was isolated from oil-macerated garlic extract by silica gel column chromatography and preparative TLC. From the results of NMR, IR, and MS analyses, its structure was determined as E-4,5,9-trithiadeca-1,7-diene-9-oxide (iso-E-10-devinylajoene, iso-E-10-DA). This compound was different from E-4,5,9-trithiadeca-1,6-diene-9-oxide (E-10-devinylajoene, E-10-DA) only in the position of a double bond. Iso-E-10-DA had antimicrobial activity against Gram-positive bacteria, such as Bacillus cereus, B. subtilis, and Staphylococcus aureus, and yeasts at the concentration lower than 100 micrograms/ml, but Gram-negative bacteria were not inhibited at the same concentration. The antimicrobial activity of iso-E-10-DA was inferior to those of similar oil-macerated garlic extract compounds such as E-ajoene, Z-ajoene, and Z-10-DA. From these results, it was suggested that trans structure and/or the position of double bond of iso-E-10-DA reduce the antimicrobial activity. (+info)The effect of antibiotic resistance on the outcome of three 1-week triple therapies against Helicobacter pylori. (4/269)
BACKGROUND: Resistance of Helicobacter pylori to antibiotics may be a major reason for treatment failure. AIM: To evaluate the effect of primary H. pylori resistance to antibiotics on the cure rates of three anti-H. pylori 1-week triple therapies. METHODS: One hundred and sixteen consecutive patients diagnosed H. pylori-positive by gastric histology, rapid urease test and culture were enrolled. Activity of tested antibiotics was determined by means of the E-test. Patients were treated for 7 days with: (i) pantoprazole 40 mg o.d. plus amoxycillin 1 g b.d. and metronidazole 250 mg q.d.s. (PAM); (ii) pantoprazole 40 mg o.d. plus clarithromycin 250 mg b.d. and metronidazole 250 mg q.d.s. (PCM); or (iii) pantoprazole 40 mg o.d. plus amoxycillin 1 g b.d. and clarithromycin 250 mg b.d. (PAC). Two months after completion of therapy, endoscopy and gastric biopsies were repeated. RESULTS: Primary resistance rates to metronidazole, clarithromycin and amoxycillin were 17.2, 6.9 and 0%, respectively. Overall H. pylori cure rates expressed as intention-to-treat and per protocol analyses were, respectively, 79% and 86% with PAM, 82% and 89% with PCM, and 85% and 85% with PAC. Significantly lower cure rates were observed in metronidazole-resistant patients treated with PAM (56% vs. 96%, P = 0.01) or PCM (50% vs. 97%, P = 0.01). A trend towards lower H. pylori cure rates was observed in clarithromycin-resistant patients treated with PCM (67% vs. 91%, P = 0.74) or PAC (50% vs. 87%, P = 0.68). CONCLUSION: Primary resistance to metronidazole influences the H. pylori cure rate of anti-H. pylori proton pump inhibitor-based triple therapies which include this antibiotic. A similar trend exists for primary clarithromycin resistance. (+info)In vitro sulfoxidation of aldicarb by hepatic microsomes of channel catfish, Ictalurus punctatus. (5/269)
The carbamate pesticide, aldicarb, demonstrates significant acute toxicity in mammals, birds, and fish, and is readily biotransformed by most organisms studied. Metabolic products of aldicarb include the more toxic sulfoxide and the less toxic sulfone as two of the major products. Both the cytochrome P450 (CYP) and the flavin monooxygenase systems (FMO) are involved in this process. This study examined the capacities of liver microsomes of male channel catfish (Ictalurus punctatus), which lack FMO, to biotransform aldicarb in vitro. In addition, the acetylcholinesterase inhibitory potencies of aldicarb and its sulfoxide and sulfone derivatives were determined. For metabolism studies, incubations of [14C]-aldicarb (0.1mM) were carried out for up to 15-90 min using 1.0 mg/mL of hepatic microsomal protein. Total NADPH- dependent biotransformation was low (< 3.0% conversion to polar metabolites), and was inhibited by carbon monoxide. The only metabolite detected was aldicarb sulfoxide (Kmapp = 53.8 +/- 25.3 microM; Vmaxapp = 0.040 +/- 0.007 nmol/min/mg). Treatment of fish with the CYP modulators beta-naphthoflavone (BNF, 50 mg/kg) and ethanol (EtOH, 1.0% aqueous) had no effect on sulfoxide production. No correlation existed between CYP isoform expression (determined by western blot) and aldicarb sulfoxidation rates, suggesting the involvement of an unmeasured CYP isoform or involvement of several isoforms with low specificity. This study indicates that a low rate of bioactivation of aldicarb to aldicarb sulfoxide may be responsible for the resistance of channel catfish to aldicarb toxicity relative to that of other piscine species. (+info)Evidence that a functional fertilin-like ADAM plays a role in human sperm-oolemmal interactions. (6/269)
Fertilin is a protein initially identified in guinea pig spermatozoa; it is the prototype of a larger family of conserved, proteins designated as a disintegrin and a metalloproteinase (ADAM). These heterodimers which consist of alpha and beta subunits, containing metalloproteinase-like and disintegrin-like domains, appear to play a role in mammalian fertilization. Peptides derived from the disintegrin domains of two ADAMs, fertilin and cyritestin, interfere with gamete adhesion and sperm-egg membrane fusion in non-human species. It has been suggested that fertilin-beta binds to an oolemmal integrin, and it is proposed that the tripeptide FEE (Phe-Glu-Glu) is the integrin recognition sequence in human fertilin-beta. We evaluated whether fertilin beta plays a role in human fertilization by studying the effects of a linear octapeptide containing the FEE sequence, SFEECDLP, and a scrambled octapeptide with the same amino acids, SFPCEDEL, on the incorporation of human spermatozoa by human zona-free eggs. The effects of G4120, a potent RGD-containing (Arg-Gly-Asp) thioether-bridged cyclic peptide which blocks both fibronectin and vitronectin receptors, and the relationship between FEE- and RGD-receptor interactions on sperm-egg interactions were also studied. The FEE-containing peptide, but not the scrampled peptide, inhibited sperm adhesion to oocytes and their penetration, over the range 1-5 microM. The inhibition induced by SFEECDLP was reversible and occurred only in the presence of peptide itself. The G4120 peptide exhibited 10-fold less inhibitory effects on sperm adhesion and penetration than did SFEECDLP. When combined, SFEECDLP and G4120 exhibited strong inhibition of both adhesion and penetration at concentrations that individually had been ineffective, suggesting co-operation between the two receptor-ligand interactions during fertilization. We propose that a fertilin-like molecule is functionally active on human spermatozoa and that its interaction with an oolemmal integrin receptor plays a role in fertilization in humans. (+info)Use of the steroid derivative RPR 106541 in combination with site-directed mutagenesis for enhanced cytochrome P-450 3A4 structure/function analysis. (7/269)
RPR 106541 (20R-16alpha,17alpha-[butylidenebis(oxy)]-6al pha, 9alpha-difluoro-11beta-hydroxy-17beta-(methylthio)androst a-4-en-3-one) is an airway-selective steroid developed for the treatment of asthma. Two metabolites produced by human liver microsomes were identified as R- and S-sulfoxide diastereomers based on liquid chromatography/mass spectrometry analysis, proton nuclear magnetic resonance, and cochromatography with standards. Sulfoxide formation was determined to be cytochrome P-450 (CYP) 3A4-dependent by correlation with CYP3A4-marker nifedipine oxidase activity, inhibition by cyclosporin A and troleandomycin, and inhibition of R- (70%) and S- (64%) sulfoxide formation by anti-3A antibody. Expressed CYP2C forms catalyzed RPR 106541 sulfoxidation; however, other phenotyping approaches failed to confirm the involvement of CYP2C forms in these reactions in human liver microsomes. Expressed CYP3A4 catalyzed the formation of the sulfoxide diastereomers in a 1:1 ratio, whereas CYP3A5 displayed stereoselectivity for formation of the S-diastereomer. The high rate of sulfoxidation by CYP3A4 and the blockage of oxidative metabolism at the electronically favored 6beta-position provided advantages for RPR 106541 over other substrates as an active site probe of CYP3A4. Therefore, oxidation of RPR 106541 by various CYP3A4 substrate recognition site (SRS) mutants was assessed. In SRS-4, A305V and F304A showed dramatically reduced rates of R-diastereomer formation (83 and 64% decreases, respectively), but S-diastereomer formation was affected to a lesser extent. A370V (SRS-5) showed decreased formation of the R-sulfoxide (52%) but increased formation of the S-diastereomer. In the SRS-2 region, the most dramatic change in sulfoxide ratios was observed for L210A. In conclusion, the structure of RPR 106541 imposes specific constraints on enzyme binding and activity and thus represents an improved CYP3A4 probe substrate. (+info)Safety and efficacy of pantoprazole 40 mg daily as relapse prophylaxis in patients with healed reflux oesophagitis-a 2-year follow-up. (8/269)
BACKGROUND: Pantoprazole is a benzimidazole derivative which selectively inhibits the proton pump H+, K+-ATPase, necessary for the final step in gastric acid secretion. AIM: To assess safety and efficacy of oral pantoprazole (40 mg o.d.) used as a prophylaxis against relapse in patients with healed reflux oesophagitis during an open-label, 2-year study. METHODS: Outpatients (n=157) with healed stage II or III reflux oesophagitis (Savary-Miller classification) were enrolled into a long-term, multicentre maintenance study. Endoscopy was performed at entry into the study, after 12 and 24 months, or when disease-specific symptoms occurred on more than three consecutive days. Symptoms were assessed at 3-monthly intervals. Endoscopically confirmed relapses (at least stage I) were evaluated as treatment failures. RESULTS: Of the 178 adverse events, experienced by 88 (56%) patients (intention-to-treat population), 12 (7%) were assessed by the investigators as possibly related to the study medication. Median serum gastrin levels increased from a baseline of 46 ng/L to 90 ng/L, reaching a plateau after 9 months. For the intention-to-treat population the endoscopic remission rates after 12 and 24 months were 87% and 76%, respectively (Life-Table survival analysis, Kaplan-Meier). CONCLUSION: Pantoprazole 40 mg proved to be safe and efficacious during a 2-year prophylaxis treatment in patients with healed reflux oesophagitis. (+info)Sulfoxides are organic compounds characterized by the functional group consisting of a sulfur atom bonded to two oxygen atoms and a carbon atom. The general structure is R-S(=O)O-R', where R and R' represent alkyl or aryl groups. They are often formed by the oxidation of sulfides, which contain a sulfur atom bonded to two carbon atoms. Sulfoxides have a trigonal pyramidal geometry at the sulfur atom due to the presence of two electron-withdrawing oxygen atoms. They exhibit properties of both polar and nonpolar compounds, making them useful as solvents and intermediates in organic synthesis.
Adrenochrome is a chemical compound that is formed when adrenaline (epinephrine) is oxidized. It is not a naturally occurring hormone or neurotransmitter, but rather a byproduct of the breakdown of these substances. The existence of adrenochrome in the human body is controversial and its effects on the human brain are not well understood.
In popular culture, adrenochrome has been associated with theories about its psychoactive properties and alleged use as a drug in illegal or illicit activities. However, there is no scientific evidence to support these claims and they should be regarded with skepticism. The misinformation surrounding adrenochrome may have originated from Hunter S. Thompson's book "Fear and Loathing in Las Vegas," where it was described as a drug that produces intense hallucinations and feelings of euphoria. However, this portrayal is not based on any scientific evidence and should be considered fiction.
Transition elements, in the context of medical definitions, refer to a group of metallic elements that are characterized by their incomplete d series of orbitals. These elements include scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), and zinc (Zn). Some definitions also include the lanthanide and actinide series.
These elements are essential to life, with iron being a key component of hemoglobin, and other transition metals playing crucial roles in various enzymatic reactions and as cofactors for many proteins. Transition elements are also widely used in medical devices, such as stainless steel implants, and in pharmaceuticals, such as platinum-based chemotherapeutic agents.
In the context of medicine and toxicology, sulfides refer to inorganic or organic compounds containing the sulfide ion (S2-). Sulfides can be found in various forms such as hydrogen sulfide (H2S), metal sulfides, and organic sulfides (also known as thioethers).
Hydrogen sulfide is a toxic gas with a characteristic rotten egg smell. It can cause various adverse health effects, including respiratory irritation, headaches, nausea, and, at high concentrations, loss of consciousness or even death. Metal sulfides, such as those found in some minerals, can also be toxic and may release hazardous sulfur dioxide (SO2) when heated or reacted with acidic substances.
Organic sulfides, on the other hand, are a class of organic compounds containing a sulfur atom bonded to two carbon atoms. They can occur naturally in some plants and animals or be synthesized in laboratories. Some organic sulfides have medicinal uses, while others may pose health risks depending on their concentration and route of exposure.
It is important to note that the term "sulfide" has different meanings in various scientific contexts, so it is essential to consider the specific context when interpreting this term.
Methionine sulfoxide reductases (MSRs) are a group of enzymes that catalyze the reduction of methionine sulfoxides back to methionine in proteins. Methionine residues in proteins can be oxidized by reactive oxygen species (ROS) or other oxidizing agents, leading to the formation of methionine sulfoxide. This modification can affect protein function and stability. MSRs play a crucial role in protecting proteins from oxidative damage and maintaining their proper function.
There are two types of MSRs, designated as MSRA and MSRB. MSRA reduces methionine-S-sulfoxides, while MSRB reduces methionine-R-sulfoxides. Both enzymes require the cofactor thioredoxin to reduce the methionine sulfoxide back to methionine. The activity of MSRs is important in various biological processes, including protein folding, stress response, and aging. Defects in MSRs have been implicated in several diseases, such as Alzheimer's disease, Parkinson's disease, and cancer.
"Pseudomonas mendocina" is a gram-negative, rod-shaped bacterium that belongs to the family Pseudomonadaceae. It is commonly found in soil and water environments. This species is generally considered to be nonpathogenic, meaning it does not typically cause disease in humans. However, there have been rare cases of infection associated with this bacterium, particularly in individuals with weakened immune systems.
The name "mendocina" comes from the location where the bacterium was first isolated, which is Mendocino County in California, USA. Like other Pseudomonas species, it can survive under a wide range of environmental conditions and can metabolize various organic compounds as its energy source.
It's worth noting that while "Pseudomonas mendocina" is not a common human pathogen, identifying the specific bacterial species involved in an infection is important for appropriate treatment. Therefore, laboratory testing and identification of bacteria to the species level can be helpful in guiding medical decision-making.
Oxidation-Reduction (redox) reactions are a type of chemical reaction involving a transfer of electrons between two species. The substance that loses electrons in the reaction is oxidized, and the substance that gains electrons is reduced. Oxidation and reduction always occur together in a redox reaction, hence the term "oxidation-reduction."
In biological systems, redox reactions play a crucial role in many cellular processes, including energy production, metabolism, and signaling. The transfer of electrons in these reactions is often facilitated by specialized molecules called electron carriers, such as nicotinamide adenine dinucleotide (NAD+/NADH) and flavin adenine dinucleotide (FAD/FADH2).
The oxidation state of an element in a compound is a measure of the number of electrons that have been gained or lost relative to its neutral state. In redox reactions, the oxidation state of one or more elements changes as they gain or lose electrons. The substance that is oxidized has a higher oxidation state, while the substance that is reduced has a lower oxidation state.
Overall, oxidation-reduction reactions are fundamental to the functioning of living organisms and are involved in many important biological processes.
Methionine is an essential amino acid, which means that it cannot be synthesized by the human body and must be obtained through the diet. It plays a crucial role in various biological processes, including:
1. Protein synthesis: Methionine is one of the building blocks of proteins, helping to create new proteins and maintain the structure and function of cells.
2. Methylation: Methionine serves as a methyl group donor in various biochemical reactions, which are essential for DNA synthesis, gene regulation, and neurotransmitter production.
3. Antioxidant defense: Methionine can be converted to cysteine, which is involved in the formation of glutathione, a potent antioxidant that helps protect cells from oxidative damage.
4. Homocysteine metabolism: Methionine is involved in the conversion of homocysteine back to methionine through a process called remethylation, which is essential for maintaining normal homocysteine levels and preventing cardiovascular disease.
5. Fat metabolism: Methionine helps facilitate the breakdown and metabolism of fats in the body.
Foods rich in methionine include meat, fish, dairy products, eggs, and some nuts and seeds.
Stereoisomerism is a type of isomerism (structural arrangement of atoms) in which molecules have the same molecular formula and sequence of bonded atoms, but differ in the three-dimensional orientation of their atoms in space. This occurs when the molecule contains asymmetric carbon atoms or other rigid structures that prevent free rotation, leading to distinct spatial arrangements of groups of atoms around a central point. Stereoisomers can have different chemical and physical properties, such as optical activity, boiling points, and reactivities, due to differences in their shape and the way they interact with other molecules.
There are two main types of stereoisomerism: enantiomers (mirror-image isomers) and diastereomers (non-mirror-image isomers). Enantiomers are pairs of stereoisomers that are mirror images of each other, but cannot be superimposed on one another. Diastereomers, on the other hand, are non-mirror-image stereoisomers that have different physical and chemical properties.
Stereoisomerism is an important concept in chemistry and biology, as it can affect the biological activity of molecules, such as drugs and natural products. For example, some enantiomers of a drug may be active, while others are inactive or even toxic. Therefore, understanding stereoisomerism is crucial for designing and synthesizing effective and safe drugs.
Oxidoreductases are a class of enzymes that catalyze oxidation-reduction reactions, which involve the transfer of electrons from one molecule (the reductant) to another (the oxidant). These enzymes play a crucial role in various biological processes, including energy production, metabolism, and detoxification.
The oxidoreductase-catalyzed reaction typically involves the donation of electrons from a reducing agent (donor) to an oxidizing agent (acceptor), often through the transfer of hydrogen atoms or hydride ions. The enzyme itself does not undergo any permanent chemical change during this process, but rather acts as a catalyst to lower the activation energy required for the reaction to occur.
Oxidoreductases are classified and named based on the type of electron donor or acceptor involved in the reaction. For example, oxidoreductases that act on the CH-OH group of donors are called dehydrogenases, while those that act on the aldehyde or ketone groups are called oxidases. Other examples include reductases, peroxidases, and catalases.
Understanding the function and regulation of oxidoreductases is important for understanding various physiological processes and developing therapeutic strategies for diseases associated with impaired redox homeostasis, such as cancer, neurodegenerative disorders, and cardiovascular disease.
Molecular structure, in the context of biochemistry and molecular biology, refers to the arrangement and organization of atoms and chemical bonds within a molecule. It describes the three-dimensional layout of the constituent elements, including their spatial relationships, bond lengths, and angles. Understanding molecular structure is crucial for elucidating the functions and reactivities of biological macromolecules such as proteins, nucleic acids, lipids, and carbohydrates. Various experimental techniques, like X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and cryo-electron microscopy (cryo-EM), are employed to determine molecular structures at atomic resolution, providing valuable insights into their biological roles and potential therapeutic targets.
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