bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclopeptin und Dehydrocyclopeptin
Authors: Framm Joachim , Nover Lutz , Azzouny Aida El , Richter Heinrich , Winter Klaus , Werner Sabine , Luckner Martin 
Published: March 2005

Feeding tritium labeled N‐methyl phenylalanine and a number of N‐methylated and unmethylated cyclic and acyclic anthranilic‐acid‐phenylalanine‐peptides, the biosynthesis of the benzodiazepine alkaloids cyclopenin and cyclopenol by Penicillium cyclopium was investigated. The results show that only the two N‐methylated cyclic peptides, cyclo‐(An‐MePhe) and 3,10‐dehydro‐cyclo‐(An‐MePhe) were incorporated without degradation and marked depression of the incorporation rate by non‐radioactive phenylalanine.The negative results with the acyclic dipeptides, N‐methylphenylalanine and cyclo‐(An‐Phe), some of which should be intermediates in the biosynthesis of cyclo‐(An‐MePhe), indicate that the formation of the latter proceeds via enzyme bound intermediates as it was found also for more complex cyclic peptide derivatives like gramicidine S. Aside the formation of the peptide bonds, the N‐methylation seems to be part of the reaction sequence on this enzyme complex, too.By looking for cyclo‐(An‐MePhe) and its dehydroderivative in cultures of P. cyclopium, two hitherto unknown benzodiazepine derivatives were isolated. Their structures were elucidated by physico‐chemical methods and comparison with synthetic material. The compounds were called cyclopeptine and dehydrocyclopeptine and identified as cyclo‐[anthranoyl‐(S)‐N‐methyl phenylalanyl] and 3,10‐trans‐dehydro‐cyclo‐[anthranoyl‐N‐methyl phenylalanyl] respectively. m‐Hydroxylated derivatives of both substances, the structure of which would correspond to that of cyclopend were not detectable.The biosyntheses of cyclopeptine and dehydrocyclopeptine from phenylalanine and the coordinated formation of both compounds together with cyclopenin and cyclopenol during the mould's idiophase further prove that they are true intermediates in the synthesis of benzodiazepine alkaloids in P. cyclopium. Cyclopeptine can be reversibly transformed into dehydrocyclopeptine.According to these and former experimental results the biosynthesis of the benzodiazepine and quinoline alkaloids of P. cyclopium seems to proceed in the following manner: The precursor amino acids (S)‐phenylalanine and anthranilic acid together with the methylgroup of methionine form an enzyme bound acyclic dipeptide intermediate (presumably an anthranoyl‐(S)‐N‐methyl phenylalanyl thioester) which undergoes cyclization to the benzodiazepin derivatives to release cyclopeptin from the enzyme. Cyclopeptin with NAD as hydrogen acceptor forms dehydrocyclopeptin in the presence of cyclopeptine dehydrogenase. Dehydrocyclopeptine by an epoxydation requiring molecular oxygen is transformed to cyclopenin, which upon m‐hydroxylation yields cyclopenol. Both, cyclopenin and cyclopenol, in the conidiospores are converted by cyclopenase to the quinoline derivatives, viridicatin and viridicatol.
Changes in the Activity of Inorganic Pyrophosphatase in a Temperature‐Sensitive DNA‐Synthesis Mutant of Escherichia coli
Authors: Heinonen Jukka , Kärenlampi Sirpa 
Published: March 2005

CRT 46, a derivative of Escherichia coli K12, has temperature‐sensitive initiation of DNA synthesis. The specific activity of inorganic pyrophosphatase in the cells of CRT46 decreased during 30 min to a new constant level (approximately 2/3 of the initial value), when DNA synthesis was arrested after 1 h at restrictive temperature 42 °C. When the culture was shifted back to permissive temperature 30 °C, the normal specific activity of the enzyme was restored in 2.5 h, while DNA was synthesized with abnormally high rate. Both the decrease and the increase in the activity of the enzyme were prevented, if protein synthesis was arrested by chloramphenical or by amino acid starvation. The activity of inorganic pyrophosphatase was stable at all temperatures up to 80 °C in the extracts of the mutant strain. Therefore the observed changes in the activity of the enzyme were evidently due to the corresponding changes in the differential rate of synthesis of the enzyme.In the cultures of the wild‐type parent strain Escherichia coli CR34 the differential rate of synthesis of inorganic pyrophosphatase was similar both at 30 °C and at 42 °C. Valyl‐tRNA synthetase was produced normally by both strains at both temperatures.The synthesis of inorganic pyrophosphatase continued normally, if DNA synthesis was prevented by nalidixic acid or thymine starvation at 30 °C in the cultures of CRT46 or both at 30 °C and at 42 °C in the cultures of CR34.By inhibiting the initiation of new rounds of DNA replication by amino acid starvation or the proceeding of DNA replication by nalidixic acid at 42 °C it was observed that the defect in the synthesis of inorganic pyrophosphatase appeared only when the rounds of DNA replication had reached the end and the temperature was restrictive.In the cultures of spontaneous revertants the differential rate of synthesis of the enzyme slowed down immediately after the shift to 42 °C, although DNA synthesis continued normally. Another derivative of CR34, BT313, which is temperature‐sensitive in the DNA synthesis, produced the enzyme with the lower differential rate both at 30 °C and at 42 °C.The results show that, although the defect in the synthesis of inorganic pyrophosphatase is somehow dependent on the defect in DNA synthesis those two phenomena are separable. Possible divA mutation, which causes the formation of DNA‐less minicells in the cultures of CRT46 at 42 °C is also responsible for the abnormal synthesis of the enzyme.
Primary Structure of Bovine Growth Hormone
Authors: Santomé José A. , Dellacha Juan M. , Paladini Alejandro C. , Peña Clara , Biscoglio Mirtha J. , Daurat Silvia T. , Poskus Edgardo , Wolfenstein Carlota E. M. 
Published: March 2005

The study of the structure of the peptides arising from native, oxidized or reduced and maleinized bovine growth hormone on incubation with trypsin, chymotrypsin and pepsin is reported.
The data obtained permitted the assembly of a unique sequence of amino acids for the poly‐peptide chain of the protein.
Various corrections and one addition to the sequence previously communicated are made.
The Subunit Structure of Yeast Pyruvate Kinase
Authors: BORNMANN Lothar , HESS Benno 
Published: March 2005

Yeast pyruvate kinase (Saccharomyces carlsbergensis) contains four identical subunits based on the following observations.1. Cyanogen bromide cleavage yields eight peptides as expected for identical subunits from the amino acid composition.2. No free N‐terminal residue could be detected. Upon acid hydrolysis 1 mole of acetate is liberated per mole of subunit. Differential hydrazinolysis indicates that anN‐acetylated terminus of the subunit is the source of the acetate molecule.3. Cleavage with carboxypeptidase A in the presence of sodium dodecylsulphate revealed that valine is the C‐terminal amino acid.
Initiation Does Not Limit the Rate of Globin Synthesis in Message‐Injected Xenopus Oocytes
Authors: LINGREL Jerry B. , WOODLAND Hugh R. 
Published: March 2005

Frog oocytes synthesize haemoglobin when injected with globin mRNA. Studies using this mRNA have shown that Xenopus oocytes have a finite unused translational capacity. When injected with roughly equal amounts of α‐and β‐globin mRNA, five times as many β chains as α chains are made. To help understand the underlying basis for these observations we have investigated the size of the polyribosomes which synthesize α‐and β‐globin after injecting various amounts of rabbit globin mRNA. Both α and β chains appear to be made on the same size of polyribosomes, whether or not the translational machinery of the cell is saturated.We interpret these results to mean that neither the defiency in α chain synthesis, nor the rate‐limiting component at saturation operates by limiting initiation. We suggest that the agent that limits total globin synthesis is a pre‐initiation “recruitment” or a “stabilisation” factor. The deficiency of α‐globin synthesis can best be explained by a partial block in elongation on the α globin mRNA.
Active Transport of Maltose in Escherichia coli K12
Authors: KELLERMANN Odile , SZMELCMAN Sevec 
Published: March 2005

A “periplasmic” maltose binding protein was purified from Escherichia coli. This protein is shown to be under the same positive control as the whole maltose system, and its synthesis is inducible by maltose. This binding protein is coded by malE, one of the three cistrons of the malB region involved in the transport of maltose.The binding characteristics of this protein, as well as the kinetics of release of bound maltose, suggest that the binding protein can exist in two states differing by their affinity towards maltose. The significance of this result is discussed in view of the role that the protein is believed to play in maltose transport.
Preparation of Highly Purified Human Chorionic Gonadotrophin by Isoelectric Focusing
Authors: QAZI Mahmood H. , MUKHERJEE Greeta , JAVIDI Kouchek , PALA Alessandro , DICZFALUSY Egon 
Published: March 2005

Highly purified human chorionic gonadotrophin, assaying 15000–17000 IU/mg in three different bioassay systems, has been obtained from a crude commercial preparation.The purification method is a simple and rapid two‐step procedure, based on preparative iso‐electric focusing on sucrose density gradient (Ampholine pH range 3–10), followed by chromatography on Sephadex G‐100. The purified gonadotrophin (mol. wt 65000), obtained from an iso‐electric pH of 4.3, moved as a single band in polyacrylamide gel electrophoresis at a pH 8.3 and showed a single precipitation line in immunoelectrophoresis.The immunological and biological activities of protein components obtained from various iso‐electric zones during fractionation are reported.
An Immunological Approach to Ferredoxin Specificity and Activity
Authors: TEL‐OR Elisha , AVRON Mordhay 
Published: March 2005

1. Antibodies to Swiss‐Chard ferredoxin were prepared and were shown to interact with plant ferredoxin and blue green algal ferredoxin, but not with clostridial ferredoxin.2. Ferredoxin‐dependent electron transport and photophosphorylation reactions were markedly inhibited by the antibodies, but N‐methylphenazonium‐methosulfate‐mediated phosphorylation was not.3. The antibody preparation inhibited endogenous cyclic and pseudocyclic photophosphorylations, in the absence of added ferredoxin.
Studies with Ubiquinone‐Depleted Submitochondrial Particles
Authors: NORLING Birgitta , GLAZEK Elzbieta , NELSON B. Dean , ERNSTER Lars 
Published: March 2005

1. The incorporation of small amounts of ubiquinone (Q) into pentane‐extracted submitochondrial particles has been studied. A procedure is described which allows nearly quantitative incorporation of as little as 0.2 to 0.3 nmol Q/mg protein, i.e. less than 10% of the Q present in the lyophilized particles prior to extraction.2. It is shown that both NADH oxidase and succinate oxidase activities can be restored to 100% of that in lyophilized particles by incorporation of 6–8 nmol Q/mg protein. The relative activities of both oxidases show a parallel response to an increase of the Q content of the particles between 0.2 and 22 nmol Q/mg protein, 50% reactivation being obtained at about 2 nmol Q/mg protein.3. 50 to 60% of the incorporated Q can be reduced by NADH or succinate, independent of the total concentration of Q in the membrane. Similar reduction values were obtained for lyophilized particles prior to extraction, suggesting that incorporated Q functions similarly to that originally present in the particles.4. Succinate dehydrogenase activity, which is decreased 50% by extraction of Q, can be completely restored upon incorporation of only 1.5 nmol Q/mg protein.5. Extraction of lyophilized particles with pentane +10% acetone results in a more effective removal of Q, but also in a differential Q requirement for NADH oxidase and succinate oxidase. Thin‐layer chromatography shows that extraction with pentane + acetone removes an additional, unidentified, nonpolar lipid.6. The present data do not support the belief that succinate oxidase and NADH oxidase communicate with separate pools of Q.
DNA‐DNA Hybridization on Nitrocellulose Filters
Authors: FLAVELL Richard A. , BIRFELDER E. Joyce , SANDERS Johan P. M. , BORST Piet 
Published: March 2005

1. The kinetics of DNA‐DNA filter hybridization have been studied using model systems. The results suggest that two limiting reactions occur.a) When the hybridization reaction is fast (i.e. with a DNA of low complexity such as phage T7 at ⋝ 5 μg DNA per filter) the reaction becomes controlled by the diffusion of DNA to the filter. This is shown by the increase in the reaction rate by shaking the hybridization vials, the inverse dependence of the rate on the molecular weight of the DNA in solution and its independence on the kinetic complexity of the DNA.b) When the hybridization reaction is slow (i.e. with a DNA of high complexity or, for T7 DNA ⋜ 2.5 μg DNA per filter disc) the reaction is limited by the hybridization reaction itself. This is shown by the inverse relationship of the hybridization rate to the complexity of the DNA and the direct proportionality of initial rate to concentration. The reaction rate is independent of shaking.2. The hybridization‐limited reaction shows two anomalies. The reaction is independent of the molecular weight of the DNA instead of the expected dependence on the square root of the molecular weight, and the calculated rate constant is nearly 10 times too low. We suggest that these anomalies result from inadequate accessibility of the DNA fixed on the filter.3. Our results provide practical guide lines to minimize competing renaturation reactions in filter hybridization experiments.
DNA‐DNA Hybridization on Nitrocellulose Filters
Authors: FLAVELL Richard A. , BORST Piet , BIRFELDER E. Joyce 
Published: March 2005

1. Comparison of DNA‐DNA filter hybridization using either denaturated duplex DNA or artificial mixtures of the two complementary strands of T7 DNA shows that the competing renaturation reaction has two effects: (a) sequestering of 20–30% of the input DNA as duplex, unavailable for hybridization, and (b) hybridization of partially renatured DNA as a concatenane to the filter‐bound DNA.2. Experiments using artificial mixtures of 32P‐labelled and 3H‐labelled L and H strands of T7 show that 10–20% of the total hybrid bound results from concatenation. With a 1:1 input ratio of complementary strands in solution, 10% of the input bound to filter DNA of a single strand (e.g. L) is of the homologous strand (i.e. L). This effect is relatively unaffected by the concentration of DNA in solution.3. Variation of the L:H ratio in solution shows that the strand in excess hybridizes and renatures more efficiently. This effect gives an underestimation of the amount of the minor strand present in solution. The numerical values obtained here are likely to be strongly dependent on the complexity of the DNA and the precise hybridization conditions.4. The implication of the results for homology experiments and determination of strand specificity in transcription is discussed.
Sandhoff Disease: Defective Glycosaminoglycan Catabolism in Cultured Fibroblasts and Its Correction by β‐N‐Acetylhexosaminidase
Authors: CANTZ Michael , KRESSE Hans 
Published: March 2005

1. Fibroblasts cultured from the skin of patients with Sandhoff disease accumulate excessive amounts of sulfated glycosaminoglycans, probably chondroitin sulfate and dermatan sulfate. In addition, Sandhoff fibroblasts show a lengthened turnover time for these compounds. Only little such abnormality in sulfated glycosaminoglycan metabolism has been found in Tay‐Sachs fibroblasts.2. The impaired catabolism of glycosaminoglycans in Sandhoff fibroblasts can be normalized, i.e. corrected, by addition of β‐N‐acetylhexosaminidase isozyme A from normal human urine to the culture medium. β‐N‐Acetylhexosaminidase isozyme B from urine is ineffective because it is not taken up by the cells. However, if homogenates of normal or Tay‐Sachs fibroblasts are used as a source of the enzymes, metabolic correction is obtained in both instances. When β‐N‐acetylhexosaminidase isozymes A and B of normal fibroblasts are separated by isoelectric focusing and tested individually, isozyme A exhibits about five times the corrective activity of isozyme B, when compared on the basis of their activity toward the synthetic substrate.3. Although β‐N‐acetylhexosaminidase isozyme B participates in the degradation of sulfated glycosaminoglycans in cultured cells, only fibroblast homogenates containing isozyme A release N‐acetylglucosamine from [14C]glucosamine‐labelled hyaluronic acid oligosaccharides in vitro.
Effects of Octanoate and Oleate on Energy Metabolism in the Perfused Rat Liver
Authors: DEBEER Luc J. , MANNAERTS Guy , DE SCHEPPER Paul J. 
Published: March 2005

The effects of octanoate and oleate were studied in the isolated fasted rat liver perfused without substrate and were compared with the effects of lactate. Measurements were made of hepatic adenine nucleotide content, formation of ketone bodies, urea and glucose and uptake of fatty acids, lactate and oxygen. Calculations of the Krebs cycle activity and the flux through the oxidation at C‐3 were carried out. Comparing the extra oxygen consumption with extra ATP needs after addition of the fatty acids or lactate, ADP: O ratios were estimated for fatty acid oxidation and lactate gluconeogenesis.1. Octanoate as well as oleate induced a net decrease in ATP and an increase in AMP content of the liver. Total adenine nucleotides were unaltered. ATP:ADP ratios were lowered while the adenylate kinase mass‐action ratio increased.2. The Krebs cycle activity was suppressed by both fatty acids and enhanced by lactate. Oxidation at C‐3 was strongly stimulated by the fatty acids and was unaffected by lactate.3. An apparent ADP:O ratio of 2.7 was obtained after lactate addition, indicating a tightly coupled oxidative phosphorylation for the liver preparations used. Octanoate and oleate gave extremely low ratios of near one and near zero respectively.4. Perfusion with oligomycin caused a severe drop in oxygen uptake by the liver, which was unaltered after addition of fatty acids. Oligomycin added after the fatty acids caused an immediate fall in oxygen uptake to the level observed with oligomycin alone. 2,4‐Dinitrophenol was able to stimulate the oligomycin‐depressed respiration, both in the absence and in the presence of fatty acids. These results indicate that under our experimental conditions the fatty acids had no uncoupling effect and that microsomal fatty acid oxidation had to be minimal.5. Incorporation of [3H]leucine into proteins in liver and medium remained unchanged after addition of fatty acids, indicating that the low apparent ADP:O ratios are not the result of an enhanced synthesis of proteins.6. The possible relationship between fatty acid transport, energy‐wasting futile cycles and the low apparent ADP:O ratios observed during fatty acid oxidation is discussed.
Depression of Reducing‐Equivalent Translocation from Substrate to Oxygen in Hepatic Metabolism of Sorbitol or Glycerol in Hypothyroidism
Authors: WERNER Harold V. 
Published: March 2005

The metabolism of sorbitol or glycerol in isolated liver cells from hypothyroid rats was studied in order to determine whether the rate of reducing‐equivalent translocation limits hepatic metabolism in a hypometabolic state. Rates of utilization of these substrates were compared with analogous data in euthyroid animals. When a saturating concentration of sorbitol or glycerol was added to the cells, gluconeogenic rates were only 54% and 29%, respectively, of the values in cells from euthyroid rats. Reducing‐equivalent translocation to O2, as well as oxygen consumption by the cells, was depressed in a similar fashion. However, addition of pyruvate, acting as a cytoplasmic hydrogen acceptor, increased the utilization of sorbitol by 1.75 μmol. g−1. min−1 and that of glycerol by 0.50 μmol. g−1. min−1. This maneuver restored sorbitol utilization equal to rates in controls, whereas it partially corrected the depression in glycerol metabolism resulting from hypothyroidism. It was inferred from the data that the disposal of hydrogen generated in the cytoplasm is a limiting factor in the metabolism of sorbitol or glycerol in hypothyroid animals. At the same time rates of gluconeogenesis from fructose or dihydroxyacetone, which utilize similar pathways, were not depressed. It was concluded that the enzymes of the gluconeogenic route are not responsible for the diminished metabolism of sorbitol or glycerol in hypothyroidism; rather a diminished capacity for hydrogen traslocation between cell compartments results in lowered rates of substrate oxidation, and subsequently, decreased rates of gluconeogenesis.Pathways of hydrogen translocation that are depressed in hypothyroidism and responsible for the decreased utilization of sorbitol or glycerol were investigated by the use of specific inhibitors. In the hypothyroid state hydrogen translocation from each substrate was depressed by 0.91–0.96 μmol. g−1. min−1. It was calculated that 82% and 88% of the depressed metabolism of sorbitol or glycerol, respectively, was due to decreased activity of a pathway insensitive to rotenone and sensitive to antimycin, most likely involving mitochondrial glycerol‐phosphate dehydrogenase. Most of the remaining loss was attributed to a diminished capacity of shuttles which were sensitive to fluoromalate and had malate dehydrogenase as a component.These studies support the concept that thyroid hormone may play an important role in the regulation of hepatic metabolism by modulating the capacities of the shuttles which translocate reducingequivalents between cell compartments.
Interaction of Ganglioside GGtet1 and Its Derivatives with Choleragen
Authors: STAERK Joseph , RONNEBERGER Hans Joerg , WIEGANDT Herbert , ZIEGLER Wolfgang 
Published: March 2005

It was confirmed that ganglioside GGtet1, i.e. Galβ1 → 3GalNAcβ1 → 4[NeuNAcα2 → 3]Galβ1 → 4Glc‐ceramide, specifically interacts with choleragen (cholera‐cxoenterotoxin) as shown by precipitate formation and inhibition of the toxicity. The isolated carbohydrate moiety of ganglioside GGtet1. i.e. GGtet1 minus ceramide, neither precipitated choleragen nor interferred with the reaction between the toxin and its antibody. However, polyacrylamide gel electrophoresis revealed a specific interaction between the sialo‐oligosaccharide and choleragen. Identical results were obtained with a sialo‐sugar derivative prepared from the carbohydrate moiety of ganglioside GGtet1 by reductive aminatio followed by N‐acetylation of its glucose unit at the reducing end.Variations in the lipohilic moiety of ganglioside GGtet1 yielded compounds (gangliosidoides) which completely retained the specific ability to precipitate choleragen, but did not interfere with its toxicity. The choleragenicity of gangliosidoide · choleragen complexes could still be abolished by ganglioside GGtet1. Polyacrylamide gel electrophoresis of galgioside · choleragen as well as gangliosidoide · choleragen complexes, in the presence of sodium dodecylsulphate, showed only the protein subunits (approx. 8000) molecular weight of the toxin to be irreversibly aggregated. When incubating canine ileal loops with ganglioside‐GGtet1 · choleragen complex or with ganglioside GGtet1 in presence of sodium deoxycholate, followed by washing of the loops with buffer after a certain period of time, an inhibition of the secretory response to a subsequent challenge with choleragen was observed. Similar treatment of ileal loops with Vibrio cholerae neuraminidase dissolved in buffer without sodium deoxycholate followed by washing of the loops, caused an enhancement as well as an inhibition of the secretory response to the subsequent challenge with choleragen depending upon the time of incubation with neuraminidase.