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At least 19 recordsLinked to original sources
PubMed1978

Effects of administration of cobalt chloride and cobalt protoporphyrin on delta-aminolevulinate synthase in rat liver.

Cobalt protoporphyrin inhibited the drug-induced increase of delta-aminolevulinate synthase as well as its transfer from the cytosol fraction to the mitochondria in rat liver in a similar way to protoheme. Cobalt chloride given to animals in a large dose exhibited similar effects. Cobalt protoporphyrin was isolated from the liver of rats treated with cobalt chloride. The observed regulatory effects of cobalt chloride with respect to the induction and the intracellular translocation of delta-aminolevulinate synthase may be mediated by cobalt protoporphyrin synthesized in vivo.

5-Aminolevulinate Synthetase↗
PubMed1978

Influence of cobalt (dietary), cobalamins, and inorganic cobalt salts on phenytoin- and cortisone-induced teratogenesis in mice.

Various cobalt-containing agents (cyanocobalamin, sodium cobaltinitrite, and cobaltous chloride), which formerly had been shown to prevent the onset of cleft palate in CF-1 mice injected with cortisone, were studied to determine whether they would afford similar protection against phenytoin. Phenytoin, however, failed to cause cleft palate in the mouse fetus when given to pregnant animals alone; and cortisone, on the contrary, induced this anomaly in the presence of the so-called cobalt antagonists as well as when administered in their absence. It is suggested from these results that high dietary intake of cobalt prevents cleft palate caused by phenytoin challenge and also negates the protective effects associated with the acute administration of cobalt compounds. Therefore, it is concluded that these well-known teratogens inhibit palatal closure in mice by different mechanisms.

Animals↗
PubMed1977

Studies on cobalt myoglobins and hemoglobins. Preparation of isolated chains containing cobaltous protoporphyrin IX and characterization of their equilibrium and kinetic properties of oxygenation and EPR spectra.

Human hemoglobin containing cobalt protoporphyrin IX or cobalt hemoglobin has been separated into two functionally active alpha and beta subunits using a new method of subunit separation, in which the -SH groups of the isolated subunits were successfully regenerated by treatment with dithiothreitol in the presence of catalase. Oxygen equilibria of the isolated subunit chains were examined over a wide range of temperature using Imai's polarographic method (Imai, K., Morimoto, H., Kotani, M., Watari, H., and Kuroda, M. (1970) Biochim. Biophys. Acta 200, 189-196). Kinetic properties of their reversible oxygenation were investigated by the temperature jump relaxation method at 16 degrees. Electron paramagnetic resonance characteristics of the molecules in both deoxy and oxy states were studies at 77K. The oxygen affinity of the individual regenerated chains was higher than that of the tetrameric cobalt hemoglobin and was independent of pH. The enthalpy changes of the oxygenation have been determined as -13.8 kcal/mol and -16.8 kcal/mol for the alpha and beta chains, respectively. The rates of oxygenation were similar to those reported for iron hemoglobin chains, whereas those of deoxygenation were about 10(2) times larger. The effects of metal substitution on oxygenation properties of the isolated chains were correlated with the results obtained previously on cobalt hemoglobin and cobalt myoglobin. The EPR spectrum of the oxy alpha chain showed a distinctly narrowed hyperfine structure in comparison with that of the oxy beta chain, indicating that the environment around the paramagnetic center (the bound oxygen) is different between these chains. In the deoxy form, EPR spectra of alpha and beta chains were indistinguishable. These observations suggest that one of the inequivalences between alpha and beta chains might exist near the distal histidine group.

Binding Sites↗
PubMed1979

Formation of cobalt protoporphyrin in the liver of rats. A mechanism for the inhibition of liver haem biosynthesis by inorganic cobalt.

1. Treatment of rats with small doses of CoCl2 decreases liver 5-aminolaevulinate synthase (EC 2.3.1.37) activity and impairs incorporation of 5-amino[14C]laevulinate into liver haem. Salts of other metals (cadmium, nickel, manganese and zinc) are all relatively inactive. 2. The dose-response curves obtained for both these effects closely mirror the accumulation in the liver of a compound that is labelled by 5-amino[14C]laevulinate and is unextractable by acetone/HCl. 3. Incorporation of 5-amino[14C]laevulinate into unextractable compound is also obtained in vitro by incubating liver homogenates with label in the presence of cobalt:isotope-dilution experiments show that the radioactivity passes through pools of porphobilinogen and protoporphyrin, but not of haem. 4. The unextractable compound is not covalently bound to protein and possesses the same extraction and spectral properties as authentic cobalt protoporphyrin. 5. It is concluded (a) that cobalt protoporphyrin is readily formed not only in vitro, but also in vivo, and (b) that its formation accounts for the impaired incorporation of 5-aminolaevulinate into haem and may also be responsible for the action of cobalt on 5-aminolaevulinate synthase.

5-Aminolevulinate Synthetase↗
PubMed1976

Cobalt bovine superoxide dismutase. Reactivity of the cobalt chromophore in the copper-containing and in the copper-free enzyme.

1. The reactivity of the zinc site of bovine superoxide dismutase has been probed by observing optical and electron paramagnetic resonance changes, under several conditions, of the Co(II)-substituted protein. 2. Only in the absence of copper are the optical and electron paramagnetic resonance spectra of the cobalt chromophore appreciably affected by alkaline pH or by cyanide. With both reagents the reaction with the copper-containing protein appears to involve the water molecule bound to the copper and does not affect the magnetic coupling between copper and cobalt. 3. The reaction of cyanide with the copper-free Co(II) protein leads to a slow detachment of cobalt from the protein as pentacyanocobalt. An oxygen adduct forms in air, analogous to that described in Co(II) carbonic anhydrase (Haffner, P. H. and Coleman, J. E. (1975) J. Biol. Chem. 250, 996--1005.) 4. Acid titration modifies the Co(II) spectra in the same way in the Cu-containing and in the Cu-free protein and brings about uncoupling of the Co(II)--Cu(II) system. Protonation of histidine-61 on the zinc facing nitrogen is suggested. 5. H2O2 modifies the cobalt chromophore only in the presence of copper. Magnetic coupling between Cu(II) and Co(II) seems to be still present after H2O2 inactivation of the enzyme.

Animals↗
PubMed1978

Studies on cobalt myoglobins and hemoglobins. Proton magnetic resonance investigation of the subunit interaction in iron-cobalt hybrid hemoglobins.

The paramagnetically shiftedd proton nuclear magnetic resonance spectra of iron-cobalt hybrid hemoglobins [alpha(Co)2beta(Fe)2 and alpha(Fe)2beta(Co)2], as well as those of deoxy forms of cobalt hemoglobin, iron hemoglobin, and their isolated chains, have been measured at 360 MHz. The proton NMR signals of the deoxy forms of iron and cobalt hemoglobins were individually assigned to each subunit. The NMR spectral characteristics of the alpha subunits in deoxycobalt hemoglobin, as well as those in deoxy-alpha(Co)2beta(Fe)2, were found to be quite different from those of beta(Co)2 subunits or isolated alpha-SH chain. Upon ligation of carbon monoxide to the beta(Fe)2 subunits in alpha(Co)2beta(Fe)2, the spectral properties of deoxy-alpha(Co)2 subunits became similar to those of the deoxy-beta(Co)2 subunits. No significant change in the NMR spectrum of the beta(Co)2 subunits was observed in alpha(Fe)2beta(Co)2 upon ligation of carbon monoxide to the alpha(Fe)2 subunits. These observations show the linkage of the electronic structure of the prosthetic groups with the subunits cooperativity in hemoglobin, as well as the inequivalence of the subunits. This is the first report on the paramagnetically shifte proton NMR spectra of the cobalt-substituted hemoproteins.

Carbon Monoxide↗
PubMed1978

Electronic properties of sulfhydryl- and imidazole-containing peptide-cobalt(II) complexes: their relationship to cobalt(II)-substituted "blue" copper proteins.

The electronic properties of 2:1 sulfhydryl- and imidazole-containing peptide-Co(II) complexes have been investigated and compared with those of Co(II)-substituted "blue" copper proteins. The Co(II) complexes of N-mercaptoacetyl-L-histidine and 3-mercaptopropionyl-L-histidine gave the ligand field parameters of deltat = 4110 and B = 756 cm(-1), and of deltat = 4120 and B = 724 cm(-1), respectively. These values correspond well to those (deltat = 4900 and B = 730 cm(-1)) of Co(II)-substituted "blue" copper proteins. The energy differences between S leads to M(II) charge transfer bands of Co(II)-Cu(II) couples were about 14,000 cm(-1) in both the proteins and the model complexes. The spectral results suggest that "blue" copper site has a pseudotetrahedral geometry and a deep absorption near 600 nm atributes to S leads to Cu(II) charge transfer.

Cobalt↗
PubMed1979

Cobalt-substituted hemoglobin Zürich (alpha 2 beta 263His leads Arg). Oxygen equilibria and EPR spectra.

Cobalt hemoglobin Zürich (alpha 2 beta 263His leads to Arg) has been successfully reconstituted from the apohemoglobin Zürich and cobaltous protoporphyrin IX. The oxygen affinity of cobalt hemoglobin Zurich, as well as that of iron hemoglobin Zürich, were measured in the absence and presence of organic phosphate and Cl-. The overall oxygen affinity of cobalt hemoglobin Zürich was found to be higher and the cooperativity as measured by the n value was smaller than those of cobalt hemoglobin A. Organic phosphate and Cl- affect the oxygen equilibrium properties of cobalt hemoglobin Zürich in a manner similar to that of cobalt hemoglobin A, but to a lesser extant than cobalt hemoglobin A. The EPR spectrum of oxy cobalt hemoglobin Zürich is less sensitive to the replacement of the buffer system from H2O to 2H2O, indicating that the hydrogen bond between the distal amino acid residue and the bound oxygen is not formed in the abnormal beta subunits. The deoxy EPR spectrum of cobalt hemoglobin Zürich is similar to that of deoxy cobalt hemoglobin A, suggesting that the deoxy cobalt hemoglobin Zürich is predominantly in the deoxy quaternary structure (T state).

Chemical Phenomena↗
PubMed1978

Oxygenation and EPR spectral properties of Aplysia myoglobins containing cobaltous porphyrins.

Cobalt myoglobins (Aplysia) have been reconstituted from apo-myoglobin (Aplysia) and proto-, meso-, and deutero-cobalt porphyrins. Each of them showed the 30--60 times lower oxygen affinity than those of the corresponding cobalt myoglobins (Sperm whale). Kinetic investigation of their oxygenation by the temperature-junp relaxation technique showed that the low oxygen affinity of cobalt myoglobin (Aplysia) is due to a large dissociation rate constant. the electron paramagnetic resonance (EPR) spectrum of oxy cobalt myoglobin (Aplysia) is affected by the replacement of H2O with D2O, suggesting a possible interaction between the bound oxygen and the neighboring hydrogen atom. A low temperature photodissociation study showed that the product of photolysis of oxy cobalt myoglobin (Aplysia) gives an EPR spectrum different from that of the deoxy-cobalt myoglobin (Aplysia) and from that of the photolysed form of oxy-cobalt myogloin (Sperm whale). These observations suggest that in oxy-cobalt myoglobin (Aplysia) the bound oxygen might interact with amino acid adjacent to it, but the interaction is weaker than that in oxy cobalt myoglobin (Sperm whale).

Animals↗