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Biomedical subjects

B Mannervik

Publications and source records attributed to B Mannervik.

At least 181 records · Page 10Linked to original sources
PubMed1985

The effect of 2,4,6-trinitrobenzenesulfonate on mercuric reductase, glutathione reductase and lipoamide dehydrogenase.

Among the three closely related enzymes, lipoamide dehydrogenase, mercuric reductase, and glutathione reductase only the latter is inhibited by 2,4,6-trinitrobenzenesulfonate (TNBS). On the other hand, all three enzymes exhibit high rates of TNBS-dependent NADPH oxidation. In the case of glutathione reductase and mercuric reductase this TNBS-dependent activity displays substrate inhibition by excess of NADPH and is strongly stimulated by NADP+. The stimulation is especially pronounced with mercuric reductase, 25-fold under some conditions. Neither substrate inhibition nor stimulation by NAD+ is observed with lipoamide dehydrogenase.

Animals↗
PubMed1985

4-Hydroxyalk-2-enals are substrates for glutathione transferase.

The 4-hydroxyalk-2-enals are established products of lipid peroxidation that are conjugated with intracellular glutathione. Cytosolic glutathione transferases from rat liver were shown to give high specific activities with 4-hydroxynonenal and 4-hydroxydecenal. The isoenzyme giving the highest specific activity was glutathione transferase 4-4. The rate of the spontaneous conjugation reaction is negligible in comparison with the rate calculated for the cellular concentration of the glutathione transferases. It is proposed that a major biological function of the glutathione transferases is to protect the cell against products of oxidative metabolism, such as epoxides, organic hydroperoxides, and 4-hydroxyalkenals.

Aldehydes↗
PubMed1985

Immunological comparison of glyoxalase I from yeast and mammals and quantitative determination of the enzyme in human tissues by radioimmunoassay.

Antibodies to glyoxalase I from yeast, rat liver, porcine erythrocytes and human erythrocytes were raised in rabbits. Gel precipitation and immunotitration experiments demonstrated that the mammalian enzymes were immunologically related, but distinct from the yeast enzyme. Fab fragments of the antibodies to human glyoxalase I did not inhibit the catalytic activity, indicating that the antigen binding sites were not directed towards the active site of the enzyme. A radioimmunoassay for glyoxalase I was developed. Quantitative analysis of human adult as well as fetal organs demonstrated that glyoxalase I was present in a concentration of approximately 0.2 micrograms/mg protein in most human tissues.

Adult↗
PubMed1985

Identification of three classes of cytosolic glutathione transferase common to several mammalian species: correlation between structural data and enzymatic properties.

The major isoenzymes of cytosolic glutathione transferase (EC 2.5.1.18) from rat, mouse, and man are shown to share structural and catalytic properties that can be used for species-independent classification. Rat, mouse, and human isoenzymes were grouped with respect to amino-terminal amino acid sequences, after correlation of seven structures analyzed in the present investigation with structures determined earlier. The isoenzymes were also characterized by substrate specificities and sensitivities to inhibitors, and the data were subjected to pattern recognition analysis. In addition, the various isoenzymes were tested for cross-reactivity by immunoprecipitation with antibodies raised against rat and human transferases. The different types of data were clearly correlated and afforded an unambiguous division of the isoenzymes into three classes named alpha, mu, and pi. Each of the three mammalian species studied contains at least one isoenzyme of each class. It is suggested that the similarities of the isoenzymes in a class reflect evolutionary relationships and that the classification applies generally.

Amino Acid Sequence↗
PubMed1984

Transformation of leukotriene A4 methyl ester to leukotriene C4 monomethyl ester by cytosolic rat glutathione transferases.

Six major basic cytosolic glutathione transferases from rat liver catalyzed the conversion of leukotriene A4 methyl ester to the corresponding leukotriene C4 monomethyl ester. Glutathione transferase 4-4, the most active among these enzymes, had a Vmax of 615 nmol X min-1 X mg protein-1 at 30 degrees C in the presence of 5 mM glutathione. It was followed in efficiency by transferase 3-4 which had a Vmax of 160 nmol X min-1 X mg-1 under the same conditions. Transferases 1-1, 1-2, 2-2 and 3-3 had at least 30 times lower Vmax values than transferase 4-4.

Animals↗
PubMed1984

Metal dissociation constants for glyoxalase I reconstituted with Zn2+, Co2+, Mn2+, and Mg2+.

Metal dissociation constants for glyoxalase I from human erythrocytes were determined by use of nitrilotriacetic acid as a metal buffer. The constants for Zn2+, Co2+, Mn2+, and Mg2+ were (2.7 +/- 0.3) X 10(-11) M, (3.0 +/- 0.8) X 10(-10) M, (4.9 +/- 0.5) X 10(-9) M, and (1.0 +/- 0.2) X 10(-6) M, respectively, demonstrating that the natural cofactor, Zn2+, has the highest affinity for the apoprotein. The results are consistent with the proposal of nitrogen and oxygen atoms as ligands to the metal in the active site of glyoxalase I. In the application of the metal buffer technique, it was found that both 1:1 and 1:2 complexes of the metal ions and nitrilotriacetic acid have to be considered.

Cobalt↗
PubMed1984

NMR and computer modeling studies of the conformations of glutathione derivatives at the active site of glyoxalase I.

The conformations of four derivatives of glutathione bound at the active site of the metalloenzyme glyoxalase I have been determined by NMR measurements and by computer model building using a distance geometry approach. Paramagnetic effects of Mn2+-glyoxalase I on the longitudinal relaxation rates of the carbon-bound protons of the substrate analog S-(acetonyl)-glutathione at three frequencies, the hydrophobic competitive inhibitor S-(propyl)glutathione at four frequencies, and the charged competitive inhibitor S-(carboxymethyl)glutathione at a single frequency were used to calculate Mn2+ to proton distances in each complex. These and previously determined distances from Mn2+ to the protons and 13C-enriched carbon atoms of the product S-(D-lactoyl)glutathione were used in a distance geometry program to compute the conformations of each enzyme-bound derivative which best fit the measured distances and other known constraints such as bond lengths, van der Waals radii, planar and trans-peptide bonds, and thioester linkages. The distance geometry program also provided a measure of the uniqueness of the conformations consistent with the experimental data. Extended Y-shaped conformations were detected for each of the bound glutathione derivatives, similar to the x-ray structure and the theoretically calculated conformation of glutathione itself, suggesting this to be a low energy form. Acceptable conformations of each enzyme-bound derivative fell into two classes with the metal either above or below the mean plane through the glutathione compound. The conformational uncertainty within each class was relatively small, ranging from deviations of 0.9-1.9 A in the average positions of each of the atoms. A small but significant difference in the conformation of the substrate analog as compared to the product was detected in the position of the reaction center carbon directly bonded to the glutathione sulfur atom. Unlike the second-sphere metal complexes formed by the bound substrate analog, the product, or the hydrophobic competitive inhibitor, the charged competitive inhibitor S-(carboxymethyl)glutathione binds farther from the metal, in the third coordination sphere.

Binding Sites↗
PubMed1984

2-Propylthiouracil does not replace glutathione for the glutathione transferases.

2-Propylthiouracil has been reported as replacing glutathione as a substrate for the glutathione transferases of rat liver. This observation has been examined with several homogeneous glutathione transferases that were prepared from human and rat liver by different methods in three laboratories. No evidence was obtained for 2-propylthiouracil as a substrate for glutathione transferase in the several reactions tested.

Animals↗
PubMed1984

X-ray absorption studies of the Zn2+ site of glyoxalase I.

X-ray edge and extended absorption fine structure spectra of Zn2+ at the active site of glyoxalase I have been measured. The edge spectrum reveals a simple set of transitions consistent with a 7-coordinate or distorted octahedral Zn2+ model complex. Analysis of the fine structure rules out sulfur ligands to Zn2+ and yields a best fit complex with Zn2+-N (or Zn2+-O) distances of 2.04 and 2.10 A, which are too great for tetrahedral Zn2+ coordination but are appropriate for an octahedral or more highly coordinated complex. Peaks of electron density in the Fourier-transformed region of the higher order shells at distances of 3-4 A from the Zn2+-imidazole model similar to those found with known Zn2+-imidazole model complexes, including carbonic anhydrase [Yachandra, V., Powers, L., & Spiro, T.G. (1983) J. Am. Chem. Soc. 105, 6596-6604], indicating at least two imidazole ligands to Zn2+ on glyoxalase I. Binding of the heavy atom substrate analogue S-(p-bromobenzyl)glutathione did not significantly alter the number of atoms directly bonded to Zn2+ or their distances. No evidence for coordination of the cysteine sulfur of glutathione by the Zn2+ was obtained, and no heavy atom signal from bromine was detected, indicating this atom to be greater than or equal to 4 A from the Zn2+. However, conformational changes of the imidazole ligands of Zn2+ upon binding of the substrate analogue were suggested by changes in the relative intensity of the doublet peaks at 3-4 A from the Zn2+ and assignable to imidazole.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1983

The amount and nature of glutathione transferases in rat liver microsomes determined by immunochemical methods.

The amount and nature of glutathione transferases in rat liver microsomes were determined using immunological techniques. It was shown that cytosolic glutathione transferase subunits A plus C, and B plus L were present at levels of 2.4 +/- 0.6 and 1.5 +/- 0.1 microgram/mg microsomal protein, respectively. These levels are 10-times higher than those for non-specific binding of cytosolic components judging from the distribution of lactate dehydrogenase, a cytosolic marker. The possibility that a portion of these glutathione transferases is functionally localized on the endoplasmic reticulum is discussed. A previously described microsomal glutathione transferase which is distinct from the cytosolic enzymes is present in an amount of 31 +/- 6 micrograms/mg microsomal protein.

Animals↗