The inhibition of lipid autoxidation by human caeruloplasmin.
Ontology highlight
ABSTRACT:
SUBMITTER: Al-Timimi DJ
PROVIDER: S-EPMC1183762 | biostudies-other | 1977 Nov
REPOSITORIES: biostudies-other
Similar Datasets
Project description:Polyunsaturated fatty acids (PUFAs) undergo autoxidation and generate reactive carbonyl compounds that are toxic to cells and associated with apoptotic cell death, age-related neurodegenerative diseases, and atherosclerosis. PUFA autoxidation is initiated by the abstraction of bis-allylic hydrogen atoms. Replacement of the bis-allylic hydrogen atoms with deuterium atoms (termed site-specific isotope-reinforcement) arrests PUFA autoxidation due to the isotope effect. Kinetic competition experiments show that the kinetic isotope effect for the propagation rate constant of Lin autoxidation compared to that of 11,11-D(2)-Lin is 12.8 ± 0.6. We investigate the effects of different isotope-reinforced PUFAs and natural PUFAs on the viability of coenzyme Q-deficient Saccharomyces cerevisiae coq mutants and wild-type yeast subjected to copper stress. Cells treated with a C11-BODIPY fluorescent probe to monitor lipid oxidation products show that lipid peroxidation precedes the loss of viability due to H-PUFA toxicity. We show that replacement of just one bis-allylic hydrogen atom with deuterium is sufficient to arrest lipid autoxidation. In contrast, PUFAs reinforced with two deuterium atoms at mono-allylic sites remain susceptible to autoxidation. Surprisingly, yeast treated with a mixture of approximately 20%:80% isotope-reinforced D-PUFA:natural H-PUFA are protected from lipid autoxidation-mediated cell killing. The findings reported here show that inclusion of only a small fraction of PUFAs deuterated at the bis-allylic sites is sufficient to profoundly inhibit the chain reaction of nondeuterated PUFAs in yeast.
| S-EPMC3437768 | biostudies-literature
Project description:1. The reversible inhibition of the oxidase activity of caeruloplasmin by cyanide was investigated. 2. The kinetics are unusual, being competitive but with the inhibited complex formed only during cycling. 3. Inhibitory concentrations of cyanide are comparable with that of caeruloplasmin. 4. One azide group completely inhibits a caeruloplasmin molecule but two cyanide groups are required. 5. The results suggest that azide binds to a half-reduced or fully reduced conformational isomer of the enzyme whereas cyanide binds to completely reoxidized isomers, and that inhibited complexes contain ligand bridges between copper atoms.
| S-EPMC1198594 | biostudies-other
Project description:1. The inhibition of the oxidase activity of caeruloplasmin by azide was investigated at 25 degrees and 7.5 degrees . 2. The inhibition is reversible on dilution or Sephadex treatment, indicating a caeruloplasmin-azide complex. 3. The enzyme is protected against azide inhibition by chloride, acetate or EDTA, the last-named acting not by chelation but by a non-specific effect similar to that of acetate. 4. Lineweaver-Burk plots with different concentrations of azide are parallel. This may occur either when the enzyme-substrate complex or when a subsequent intermediate structure of the enzyme forms the inhibited complex. 5. At 7.5 degrees inhibition may be shown not to occur until after the initial reaction of enzyme with substrate. 6. At 7.5 degrees , the inhibition is of the mutual-depletion type, inhibitory concentrations of azide being comparable with the concentration of caeruloplasmin. It is shown that the binding of a single azide group completely inhibits a caeruloplasmin molecule. 7. An arrangement of the four valence-changing copper atoms of caeruloplasmin is proposed in which they are so close together in the cuprous form that reoxidation may occur by the simultaneous transfer of four electrons from the copper atoms to a single oxygen molecule.
| S-EPMC1265135 | biostudies-other
Project description:Nitroxides are putative intermediates in the accepted reaction mechanisms of the diarylamine and hindered amine antioxidants that are universally added to preserve synthetic and natural hydrocarbon-based materials. New methodology which enables monitoring of hydrocarbon autoxidations at low rates of radical generation has revealed that diarylnitroxides and hindered nitroxides are far better inhibitors of unsaturated hydrocarbon autoxidation than their precursor amines, implying intervention of a different mechanism. Experimental and computational investigations suggest that the nitroxides catalyze the cross-dismutation of hydroperoxyl and alkylperoxyl radicals to yield O2 and a hydroperoxide, thereby halting the autoxidation chain reaction. The hydroperoxyl radicals - key players in hydrocarbon combustion, but essentially unknown in autoxidation - are proposed to derive from a tunneling-enhanced intramolecular (1,4-) hydrogen-atom transfer/elimination sequence from oxygenated radical addition intermediates. These insights suggest that nitroxides are preferred additives for the protection of hydrocarbon-based materials from autoxidation since they exhibit catalytic activity under conditions where their precursor amines are less effective and/or inefficiently converted to nitroxides in situ.
| S-EPMC6053651 | biostudies-literature
Project description:The autoxidation reactions of 2-acyl-2,3-dihydroquinazolin-4(1H)-ones 4a and 5a and 2,2'-bis(dihydroquinazolinone) 6a are described. These reactions generate aminyl radicals that undergo β-C-C cleavage, and subsequent reactions of the resulting C-based radicals with O2 lead to diverse products with good selectivity, depending on the structure of the substrate. Oxidation of 4a, in which the 2-acyl group is part of a cyclic acenaphthenone unit, yields a heterocyclic C-hydroperoxylaminal via 1,2-acyl migration. Oxidation of 5a, which contains a 2-acetyl group, yields peracetic acid and a quinazolinone product. Oxidation of 6a forms a bis(quinazolinone) by net dehydrogenation.
| S-EPMC6641016 | biostudies-literature
Project description:The blue copper protein caeruloplasmin is synthesized mainly by hepatocytes. An alternative transcript for caeruloplasmin produced in certain extrahepatic tissues, CP-1, contains an additional 12 nucleotides encoding 4 amino acids not present in the hepatic transcript, CP-2 [Yang, Friedrichs, Cupples, Bonifacio, S Sanford, Horton & Bowman (1990) J. Biol. Chem. 265, 10780-10785]. We have demonstrated transcription of caeruloplasmin mRNA by a well-differentiated human uterine epithelial adenocarcinoma cell line, Ishikawa, and by human uterine endometrium and purified endometrial glands. Identical CP-2 nucleotide sequences were obtained for partial caeruloplasmin transcripts from human liver and Ishikawa cells, indicating that CP-2 transcripts are produced by uterine epithelial lining cells. The synthesis of caeruloplasmin protein was demonstrated for Ishikawa cells and another uterine adenocarcinoma cell line, ECC1. Peptide-mapping analysis indicated that caeruloplasmin secreted by Ishikawa cells was structurally identical with the protein synthesized by the human hepatoblastoma cell line HepG2. The secretion of a 135,000-M(r) caeruloplasmin by Ishikawa and ECC1 cells, comparable with that of the human hepatoblastoma cell line, HepG2, indicated similar processing of uterine and hepatic caeruloplasmin. Incorporation of 67Cu into caeruloplasmin was demonstrated for Ishikawa and ECC1 cells, suggesting that the human uterus produces a bioactive form of caeruloplasmin and possesses the necessary metal transporters and intracellular machinery for copper incorporation into this protein.
| S-EPMC1132061 | biostudies-other
Project description:Atmospheric autoxidation of volatile organic compounds (VOC) leads to prompt formation of highly oxidized multifunctional compounds (HOM) that have been found crucial in forming ambient secondary organic aerosol (SOA). As a radical chain reaction mediated by oxidized peroxy (RO2) and alkoxy (RO) radical intermediates, the formation pathways can be intercepted by suitable reaction partners, preventing the production of the highest oxidized reaction products, and thus the formation of the most condensable material. Commonly, NO is expected to have a detrimental effect on RO2 chemistry, and thus on autoxidation, whereas the influence of NO2 is mostly neglected. Here it is shown by dedicated flow tube experiments, how high concentration of NO2 suppresses cyclohexene ozonolysis initiated autoxidation chain reaction. Importantly, the addition of NO2 ceases covalently bound dimer production, indicating their production involving acylperoxy radical (RC(O)OO•) intermediates. In related experiments NO was also shown to strongly suppress the highly oxidized product formation, but due to possibility for chain propagating reactions (as with RO2 and HO2 too), the suppression is not as absolute as with NO2. Furthermore, it is shown how NO x reactions with oxidized peroxy radicals lead into indistinguishable product compositions, complicating mass spectral assignments in any RO2 + NO x system. The present work was conducted with atmospheric pressure chemical ionization mass spectrometry (CIMS) as the detection method for the highly oxidized end-products and peroxy radical intermediates, under ambient conditions and at short few second reaction times. Specifically, the insight was gained by addition of a large amount of NO2 (and NO) to the oxidation system, upon which acylperoxy radicals reacted in RC(O)O2 + NO2 ? RC(O)O2NO2 reaction to form peroxyacylnitrates, consequently shutting down the oxidation sequence.
| S-EPMC6251564 | biostudies-literature
Project description:[reaction: see text] Treatment of salvinorin A (1a) with KOH in MeOH gave the enedione 3, for which the dienone structure 7 was recently proposed. Also isolated, after methylation, were the secotriesters 4a-c. A mechanism for this unusual series of autoxidations is proposed. Surprisingly, 4a showed weak affinity at the kappa-opioid receptor. Divinatorins A-C (2a-c) showed no affinity at opioid receptors. Attempted reduction of 3 to a novel salvinorin diol (9d) was unsuccessful, but careful deacetylation of salvinorin C (9a) provided a viable route to this compound. A general method for identifying salvinorin 8-epimers by TLC is also presented.
| S-EPMC2778035 | biostudies-literature
Project description:No Cu(II) ion is measurable in human serum or synovial fluid by the phenanthroline assay. On storage of human serum or synovial fluid at 4 degrees C, phenanthroline-detectable copper appears, lipid peroxidation occurs, ferroxidase I activity declines and ferroxidase II activity rises, yet there is no fall in immunologically detectable caeruloplasmin. Storage of body fluids at -20 degrees C or -70 degrees C slows, but does not prevent, these deteriorative changes. It is suggested that the presence of low-molecular-mass Cu(II) ion complexes, ferroxidase II activity, "cytotoxic factors' and "immunosuppressive factors' in body fluids may be, in part or in whole, an artifact of the storage and handling of the fluids. A report [Blake, Blann, Bacon, Farr, Gutteridge & Halliwell (1983) Clin. Sci. 64, 551-553] that the caeruloplasmin present in rheumatoid synovial fluid is deficient in ferroxidase activity is shown to be such an artifact. It is strongly recommended that all such experiments be performed upon freshly taken fluid samples.
| S-EPMC1152645 | biostudies-other
Project description:The increasing prevalence of amyloid-related disorders, such as Alzheimer's or Parkinson's disease, raises the need for effective anti-amyloid drugs. It has been shown on numerous occasions that flavones, a group of naturally occurring anti-oxidants, can impact the aggregation process of several amyloidogenic proteins and peptides, including amyloid-beta. Due to flavone autoxidation at neutral pH, it is uncertain if the effective inhibitor is the initial molecule or a product of this reaction, as many anti-amyloid assays attempt to mimic physiological conditions. In this work, we examine the aggregation-inhibiting properties of flavones before and after they are oxidized. The oxidation of flavones was monitored by measuring the UV-vis absorbance spectrum change over time. The protein aggregation kinetics were followed by measuring the amyloidophilic dye thioflavin-T (ThT) fluorescence intensity change. Atomic force microscopy was employed to image the aggregates formed with the most prominent inhibitors. We demonstrate that flavones, which undergo autoxidation, have a far greater potency at inhibiting the aggregation of both the disease-related amyloid-beta, as well as a model amyloidogenic protein-insulin. Oxidized 6,2',3'-trihydroxyflavone was the most potent inhibitor affecting both insulin (7-fold inhibition) and amyloid-beta (2-fold inhibition). We also show that this tendency to autoxidize is related to the positions of the flavone hydroxyl groups.
| S-EPMC8465893 | biostudies-literature