Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: HUMANGGP:001372 (ESR)
 7,313 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Optical and ESR spectra of erythrocyte superoxide dismutase denaturated with acid and alkali are described. Sharp changes in activity and spectra were found. "Residual" activity of alkaline denaturated protein was higher than of acidic denaturated sample. It is suggested that covalent bonding copper-nitrogen is essential for superoxide dismutase activity of the protein or synthetic copper complexes.
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PMID:[Acid and alkaline denaturation of superoxide dismutase]. 0 Oct 99

The progesterone-induced purple phosphatase isolated from the uterine flushings of pigs is activated by a variety of reagents that cleave disulfide bonds, including 2-mercaptoethanol, dithiothreitol, L-ascorbate, L-cysteine, sulfite, and cyanide. It is inhibited by various mercurials, iodoacetamide, O-iodosobenzoate, and hydrogen peroxide. Thiols increase the specific phosphatase activity from 25 to about 300 units per mg of enzyme. This activation is accompanied by a shift in the extinction maximum to higher energy to yield a protein with a pink coloration. Following maximum activation there is a gradual decrease in enzyme activity and protein color which is accompanied by loss of ferrous iron from the protein. Sodium dithionite at 10 mM or higher causes an immediate inhibition of phosphatase activity and bleaching of color, and can be used to prepare the iron-free apoprotein. The latter can be partially reactivated by Fe3+ salts but not by Fe2+. The Fe3+ restores the pink form of the enzyme with a specific activity of about 200 units/mg of protein. Cu2+ also causes some reactivation, but other metal ions were ineffective. ESR studies showed that the pink form of phosphatase contains approximately 1 atom of high spin ferric iron per molecule. It is concluded that the phosphatase requires a free thiol and Fe3+ for activity. Reduction of the iron leads to complete loss of both color and enzyme activity. The color change from purple to pink represents disulfide reduction and is not due to reduction of iron.
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PMID:Requirement of an essential thiol group and ferric iron for the activity of the progesterone-induced porcine uterine purple phosphatase. 0 64

The complexation behaviour of Cu(II) with di- and tripeptides containing the aromatic amino acids phenylalanine or typtophan has been investigated at different pH-values and compared with results obtained with di- and triglycine. The results obtained by means of ESR and optical absorption spectroscopy show an influence of the two different aromatic entities on the magnetic and optical parameters. A significant decrease of the g11-value and, concomittantly, an increase of the energy of the d-d transition was measured when an aromatic entity is present in the peptide. A possible explanation for this observation is given.
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PMID:On the influence of aromatic residues on the interaction of copper (II) with small peptides containing aromatic amino acids: ESR and optical studies. 2 Jul 6

Using a combination of ultraviolet-visible absorption, 1H NMR and ESR techniques we have established that N(1) of the imidazole and N(1) of the pyrimidine residues of bleomycin A2 bind to Cu(II) and Zn(II). The observations coupled with the earlier results that the alpha-amino group of the alpha-amino carboxamide function and the carbamoyl moiety are also Cu(II)-ligating groups makes it possible to reconstruct the detailed geometry and stereochemistry of the metal binding site of bleomycin A2.
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PMID:A spectroscopic investigation of the metal binding site of bleomycin A2. The Cu(II) and Zn(II) derivatives. 7 23

High resolution electron spin resonance spectra of the stepwise formation of CN- complexes of Co(II) and Cu(II) carbonic anhydrase show that both metal enzymes form successive 1:1 and 2:1 addition products with CN- at 112 K. The 1:1 complex with the Cu(II) enzyme has a rhombic ESR spectrum similar to the spectra of the 1:1 complexes of the Cu(II) enzyme with CH3COO-, OCN-, N3-, and SH-. The 1:1 complex with the CO(II) enzyme shows a broad resonance at 10 K indicating the presence of high spin Co(II). Previous optical, ESR, and magnetic susceptibility data suggest that the 1:1 complexes are 4-coordinate. At high concentrations of 13CN- the Cu(II) enzyme forms a 2:1 CN- complex with a shift to an axial ESR signal showing ligand nuclear superhyperfine structure from two magnetically equivalent equatorial nitrogen nuclei of the protein and two magnetically equivalent equatorial carbon ligands from two 13CN- anions. Under the same conditions a structurally analogous dicyanide complex of the co(II) enzyme forms with the appearance of and axial ESR signal typical of low spin Co(II). Ligand nuclear superhyperfine structure shows the presence of an axial protein nitrogen as ligand and two magnetically equivalent equatorial carbon ligands from two 13CN- anions. The dicyanide complexes of the Co(II) and Cu(II) enzymes form completely only in frozen solutions and analysis of the ESR spectra show them to have a 5-coordinate square pyrimidal geometry. Comparison of the ligand superhyperfine structure on the ESR signals of both dicyanide complexes shows that there are three nitrogen nuclei of the protein present as ligands at the metal binding site; one axial and two equatorial in the dicyanide complexes. A transient 5-coordinate intermediate might play a role in the mechanism of action of carbonic anhydrase by facilitating ligand exchange reactions within the inner coordination sphere of the Zn(II) ion at the active center.
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PMID:Structure of the active site of carbonic anhydrase as determined by electron spin resonance. 16 45

1. Dialysis against cyanide at pH 7 of Achromobacter cycloclastes nitrite reductase [EC 1.7.99.3] of a dissimilatory type led to the removal of about 50% of the copper from the enzyme molecule, with a concomitant decrease of the enzymatic activities. It was inferred that enzyme-bound copper atoms play an essential role in the catalytic activities of the enzyme. 2. The amino acid composition of the enzyme was determined after acid hydrolysis. 3. ESR spectra of the frozen solution and lyophilized powder of the nitrite reductase predominantly showed the presence of two kinds of copper: Type 1 Cu2+, which had narrow and sharp hyperfine splitting, and Type 2 Cu2+, which had broader hyperfine splitting. The bond between the oxidized enzyme and nitrite seems to be ionic.
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PMID:Achromobacter cycloclastes nitrite reductase. The function of copper, amino acid composition, and ESR spectra. 17 83

The complex ESR signal previously observed in fatty tissues has been identified. It is a copper low-molecular-weight sulphur compound complex similar to copper-dithiocarbamate. The usual source of this signal is contact of copper-containing tissue with surgeon's gloves. This result emphasizes the care that must be taken in obtaining and interpreting ESR spectra of tissues. The formation of this complex by intentionally adding dithiocarbamate to tissue can be used as a very simple and sensitive analytical method for tissue copper. Copper levels of less than 0-1 ppm can be detected by this method. This is an order of magnitude more sensitive than determinations by atomic absorption.
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PMID:Experimental considerations in biological ESR studies. I. Identity and origin of the 'tissue lipid signal': a copper-dithiocarbamate complex. 18 81

Electron spin resonance and optical absorption studies have been done in order to investigate the interaction between Cu2+ and aromatic amino acids in aqueous solution at 77 K and at room temperature as well. Depending on the concentration each aromatic amino acid can form two different kinds of complexes with Cu2+ which can be characterized by its ESR pattern. Additional information was obtained from optical d-d and CT transitions.
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PMID:ESR and optical absorption studies on the copper (II) interaction with aromatic amino acids. 18 47

Previous results indicate that a tryptophan residue(s) may interact with the sugar substrate and Cu(II) atom of galactose oxidase (Ettinger, M. J., and Kosman, D. J. (1974), Biochemistry 13, 1248). We now show that N-bromosuccinimide (NBS) reduces enzymatic activity to 2% as two tryptophans are oxidized; only four residues are easily oxidized in the holoenzyme. An enzymatic activity vs. number of residues oxidized profile suggests that this inactivation is probably associated with only one of the first 2 residues oxidized. There is no evidence for chain cleavage or modification of amino acids other than tryptophan. While substrate protection is not afforded by the sugar substrate, the activity-related tryptophan is placed within the active-site locus by spectral evidence. NBS oxidation of two tryptophans results in a marked diminution of the large copper optical-activity transition at 314 nm. Under some reaction conditions, a doubling of ellipticity in the 600-nm region of copper CD is also observed. The effects of the NBS oxidation on the CD spectra of galactose oxidase permit the assignment of the 314-nm CD band to a charge-transfer transition and the 229-nm extremum to a specific tryptophan contribution. The AZZ parameter from electron spin resonance spectra is also markedly reduced by the NBS oxidation. Moreover, while cyanide binds to the native enzyme without reducing the Cu(II) atom, cyanide rapidly reduces the Cu(II) atom to Cu(I) in the NBS-oxidized enzyme. These CD and ESR results are taken to suggest that one aspect of the inactivation by NBS oxidation may be a conversion of the pseudosquare planar copper complex in the native enzyme to a more distorted, towards tetrahedral, complex in the inactivated enzyme. Since the inactivation can be accomplished without affecting binding of the sugar substrate, tryptophan oxidation must affect catalysis per se.
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PMID:Role of tryptophan in the spectral and catalytic properties of the copper enzyme, galactose oxidase. 19 67

Exposure of aqueous glasses of Cancer magister haemocyanin to 60Co gamma-rays at 77 K results in a novel paramagnetic centre with ESR features showing hyperfine coupling to one strongly coupled 63/65 Cu nucleus and possibly one weakly interacting 63/65 Cu nucleus. Addition of electron scavengers showed that this centre is formed by electron addition. It is suggested that addition occurs at Cu2+-O2-Cu2+ units to give Cu2+-O2Cu+ centres. If this is correct, then electron-transfer between the two copper ions is slow or non-existent, possibly indicating that they are inequivalent. The centre is unstable, the signals being lost irreversibly on heating to approx. 270 K. The g parallel and A parallel (63/65Cu) data place this centre into the type I classification.
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PMID:Electron addition to the active site of Cancer magister haemocyanins. An ESR study of cu(II) centres after gamma-radiolysis. 20 25


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