Biomedica biochimica acta (Biomed Biochim Acta)

Publisher: Akademie der Wissenschaften der DDR. Presidium; Deutsche Gesellschaft für Experimentelle Medizin

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Other titles Biomedica biochimica acta
ISSN 0232-766X
OCLC 9681158
Material type Periodical
Document type Journal / Magazine / Newspaper

Publications in this journal

  • [Show abstract] [Hide abstract]
    ABSTRACT: Hemorrhagic toxin e (Ht-e), a metalloproteinase isolated from the venom of the Western Diamondback rattlesnake Crotalus atrox, digests laminin and nidogen, both in their isolated forms and when present in a purified soluble complex. The only common site of cleavage by Ht-e of isolated nidogen and nidogen when complexed with laminin is at amino acid residue 336 in the amino terminal domain. Additionally, nidogen in complex with laminin is also cleaved at sites 322, 351 and 840 as determined by sequence analysis and site 953 as proposed from the molecular mass of a digestion product. Isolated nidogen, on the other hand, was cleaved at amino acid residues 75, 336, 402, and 920, as determined by sequence determinations and approximately at residues 296, 478, 625 and 702 as proposed from the molecular mass values of the generated polypeptide chains. Products from the proteolytic cleavage of the A and B2 chains of laminin were observed with the sites of cleavage determined to be at position 2666 in the laminin A chain and position 1238 in the laminin B2 chain. The laminin digestion products were identical regardless of whether nidogen was present in a complex with the laminin chains.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The ratio of hydrolysis to aminolysis product in papain-catalyzed acyl transfer reactions using various nucleophiles was determined. The data are interpreted in terms of binding specificity. The acyl transfer reactions were performed using the acyl donor Mal-Phe-Ala-OEtCl. The analysis of the structure-activity relationships of the hydrophobic S1'-P1' contact indicates that the S1' subsite can accommodate maximally three methyl(ene) groups. Hydrophilic amino acid side chains are better bound to S1' than can be explained by their hydrophobicities. The S2' as well as the S3' binding subsite exhibits a preference for space-filling hydrophobic amino acid residues.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Autophagy is a non-selective bulk process for degradation of cytoplasm, as indicated by ultrastructural evidence and by the similarity in autophagic sequestration rates of various cytosolic enzymes with different half-lifes. The initial autophagic sequestration step is subject to feedback inhibition by amino acids, an effect which is potentiated by insulin and antagonized by glucagon. Epinephrine and other adrenergic agonists inhibit autophagic sequestration through a prazosin-sensitive, alpha 1-adrenergic mechanism. The sequestration is also inhibited by cAMP and by protein phosphorylation as indicated by the effects of cyclic nucleotide analogues, phosphodiesterase inhibitors and okadaic acid. Asparagine specifically inhibits autophagic-lysosomal fusion without having any significant effects on autophagic sequestration, intralysosomal degradation or on the endocytic pathway. Autophaged material that accumulates in prelysosomal vacuoles in the presence of asparagine is accessible to endocytosed enzymes, revealing the existence of an amphifunctional organelle, the amphisome. Evidence from several cell types suggests that endocytosis may be coupled to autophagy in a differential (ligand-dependent) manner, and that amphisomes may play a central role as collecting stations for material destined for lysosomal degradation.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Human cystatins A, B and C were purified, and their inhibition efficiency was tested with the cysteine proteinase cathepsin S. Cathepsin S was strongly inhibited by cystatins A and B in the subnanomolar range and by cystatin C in the picomolar range. Two steps of inhibition of cathepsin S by the cystatins which involve slow binding are discussed.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Pepsin catalyzed peptide synthesis in biphasic systems containing more than 95% (v/v) of organic phase was studied. Good yields were only obtained with more hydrophobic solvents, in spite of the low solubility of the substrates. The effects of the following parameters were also investigated: concentration of amino and carboxylic components, pH and buffer concentration, ratio between the aqueous and organic phases. The influence of different amino acid residues in the P2 position was investigated through the coupling between Z-Xyz-Phe-OH (where Xyz = Ala, Phe, Trp and Tyr) and Phe-OMe.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Prolyl endopeptidase, an enzyme exhibiting high specificity towards the Pro-Xaa bond, is thought to play an important role in the metabolism of biologically active peptides. We have purified the enzyme from pig muscle and observed significant differences in its kinetic behavior as compared to the extensively studied serine proteases, such as chymotrypsin. Thus, pH-dependence of, and kinetic deuterium isotope effects on, the rate constants indicated that the enzyme has two forms, which exhibit different activities and interconvert with changing pH. It can be concluded that a general base/acid-catalyzed acylation step is rate-limiting in the lower pH range, and an isotopically silent step, probably a conformational change preceding the acylation dominates the reaction in the physiological pH range.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: We have examined the effects of salicylate on fluxes of lactate metabolism in rat hepatocytes using a steady state model. Salicylate produces an uncoupling effect, an inhibition of gluconeogenesis, a marked activation of pyruvate dehydrogenase flux, and an inhibition of endogenous fatty acid oxidation. Agents with known functions such as dinitrophenol and dichloroacetate were also compared in this system. The in vitro inhibition of gluconeogenesis caused by salicylate is not primarily related to the uncoupling effect. The fact that octanoate, but not palmitate, overcomes the salicylate inhibition of gluconeogenesis suggests that salicylyl CoA is involved in the inhibition. To relate in vitro studies to Reye's syndrome in vivo, in which medium chain dicarboxylic acids accumulate, we have also examined the effects of monomethyl suberate on liver lactate metabolism. This half ester is taken up by the hepatocytes, and causes inhibition of lactate gluconeogenesis, and uncoupling. Both salicylate and monomethyl suberate inhibit the oxidation of 0.2 mM octanoate by hepatocytes.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The interaction of delta (Ser50)-hirudin with alpha-thrombin has been investigated. Deletion of Ser50 of r-hirudin caused a 2.7 fold increase of the Ki for its complex with alpha-thrombin. Determination of the rate constants kon and koff for complex formation showed that this effect was mainly due to a change in koff.
    No preview · Article · Feb 1991 · Biomedica biochimica acta

  • No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The effect of four human serine proteinases on the human cysteine proteinase inhibitor, cystatin C, has been studied in vitro. Neutrophil elastase in catalytic amounts was observed to rapidly cleave cystatin C at neutral pH, thereby giving rise to a modified form of the inhibitor lacking the N-terminal Ser1-Val10 decapeptide. The two other leukocyte serine proteinases, cathepsin G and neutrophil proteinase 4, did not catalytically hydrolyse cystatin C bonds. Neither had the seminal plasma serine proteinase, prostate-specific antigen, any effect on cystatin C. The physiological implications of neutrophil elastase catalysed modification of cystatin C are discussed, and recent findings indicating that this reaction also occurs in vivo are reviewed.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The amino acid sequences of the genes coding for four multienzyme peptide synthetases, operating by the thiotemplate mechanism are compared, to show underlying principles in the biosynthetic mechanism. Alignment with other carboxylic acid activating enzymes shows the sequences. LAY(V/I)I(Y/F)TSGT(T/S)GxPKGV and GELx(L/I)GGxG(V/I) to be involved in MgATP2-binding and adenylate formation, and two other sequences, one containing the element FxLGG(H/D)S(I/L) to be involved in covalent binding of the amino acid. As a general rule, 1000 amino acid building blocks are responsible for the incorporation of one amino acid into the nascent peptide.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The transglycosylation from raffinose and lactose to Aloc-Ser-OMe is catalyzed respectively by alpha and beta galactosidases. Transglycosylation from cellobiose has been achieved with beta-glucosidase. The simplicity of the enzymatic synthesis, the stereospecificity of the condensations in one-pot reactions and the ease of purification give the method value for large scale preparation of beta-linked derivatives. The protective groups of the serine residue can be cleaved under mild conditions: the ester group has been removed quantitatively by papain catalyzed hydrolysis and the Aloc group by a Pd (0) hydrostannolytic cleavage.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Administration of stobadine, a cardioprotective substance in investigation prevents a decrease in the content of protein SH groups and glutathione in hearts of rats treated with high doses of isoproterenol (ISO) (30 mg/kg). Moreover, stobadine also attenuated the increase in the content of malondialdehyde and activities of catalase and glutathione reductase as well as a diminution in the GSH/GSSG ratio observed in heart mitochondria isolated from ISO-treated animals. Since stobadine may be considered as a scavenger of reactive oxygen species (ROS), the above effects of the latter substance support the assumption about a possible involvement of reactive oxygen species (ROS) in some processes initiated by administration of ISO in doses inducing cardiac hypertrophy. However our results also indicate that ROS-mediated processes are not necessarily involved in the mechanism of induction of cardiac hypertrophy itself.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The known proportional increase in the amplitude of the pattern reversal visually evoked potential (VEP) with increasing stimulus area does not occur for the motion-onset VEP. When the stimulus area of the total field (6 degrees x 6 degrees) is compared to that of the half-field (6 degrees x 3 degrees), the N200 amplitude of the motion-onset VEP is not changed proportionally but remains almost constant. Reducing the pattern contrast beyond the saturation value for the motion-VEP yields essentially the same results. Contrary to the pattern reversal VEP, the amplitudes of the motion-onset VEP are found to be more pronounced for the nasal than for the temporal hemiretina. Our results support the notion of a genuine difference between the pattern- and the motion-analyzing visual system.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Liver and intestinal nucleotides and energy charge levels were examined in rats at portal vein clamping for 1, 5 or 30 min and after reflow for 1 or 6 h following 30 min clamping. In both tissues, clamping resulted in a loss of ATP, energy charge, UTP, GTP, UDP-glucuronic acid and UDP-N-acetylhexosamine levels, which all, except ATP and total adenosine phosphates, essentially recovered at 1 h reflow. At 6 h reflow, liver UDP-glucuronic acid and liver glutathione decreased in both clamped and sham operated rats.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Intramolecular cross-linking of octameric yeast phosphofructokinase was applied to study the effect of substrate-imprinted conformational changes on the regulatory properties of the enzyme:Cross-linking performed in the presence of fructose 6-phosphate yields a substrate-imprinted enzyme species the affinity of which towards this substrate is significantly higher than that of native phosphofructokinase and of the enzyme cross-linked in the absence of fructose 6-phosphate. The enzyme cross-linked in the presence of fructose 6-phosphate does not exhibit cooperativity with respect to this substrate but is still activated by AMP and by fructose 2,6-bisphosphate. This activation consists in an increase of substrate affinity with respect to fructose 6-phosphate. In the absence of positive effectors, the maximum activity of the cross-linked enzyme corresponds to the respective values of native phosphofructokinase when activated by AMP or by fructose 2,6-bisphosphate. At saturating levels of AMP and of fructose 2,6-bisphosphate, nearly identical affinities with respect to fructose 6-phosphate are found, ranging between the Km values of native phosphofructokinase activated by AMP and by fructose 2,6-bisphosphate. Covalent stabilization of the substrate-imprinted enzyme conformation does not affect the interaction of phosphofructokinase with ATP at the substrate-binding site. The results suggest that the allosteric regulation of yeast phosphofructokinase is mainly related to conformational changes controlled by fructose 6-phosphate while the ATP affinity at the catalytic site of the enzyme remains essentially unaffected.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: The cDNA probes cf56a, b identify deletions in 45% of the investigated patients with Duchenne and Becker muscular dystrophy (DMD/BMD). But carrier detection by junction fragments using normal gel electrophoresis conditions separating fragments up to a size of about 25 kilobases is possible only in selected cases. We, therefore, applied separation of Sfi I-digested DNA by rotating-field gel electrophoresis (RFE) in combination with Southern blot transfer and hybridization using cf56a for this purpose. In this study we compared hybridizing fragments of DNA from three DMD families with different deletion patterns: distal to the Sfi I-site F located between exon 48/49 (family A), proximal to the Sfi I-site F including the P20 intron (family B), and bridging the Sfi I-site F (family C). Junction fragments in the DNA of 2 affected boys and their mothers were detected in families B and C. Carrier determination on this basis was performed for family C. Given these three families are representative for other families with similar deletions, it will be possible to offer carrier diagnosis using RFE in 38% of the studied families with DMD/BMD caused by deletions in the major hot spot region.
    No preview · Article · Feb 1991 · Biomedica biochimica acta
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    ABSTRACT: Calf chymosin catalyzes peptide synthesis optimally at pH 4-5 giving satisfactory yields of methyl esters or p-nitroanilides of benzyloxycarbonyl tetra- to hexapeptides, provided that hydrophobic amino acid residues form the new peptide bond. The enzyme efficiency depends also on the nature of adjacent amino acid residues. As an aspartyl proteinase with characteristic specificity pattern chymosin would be useful for synthesis of middle length peptides.
    No preview · Article · Feb 1991 · Biomedica biochimica acta

  • No preview · Article · Feb 1991 · Biomedica biochimica acta

  • No preview · Article · Feb 1991 · Biomedica biochimica acta