bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Control of Liver Glycogen Synthetase Phosphatase by Phosphorylase
Authors: Stalmans Willy , De Wulf Henri , Hers Henri‐Géry 
Published: March 2005

The activation of glycogen synthetase in a liver gel filtrate and the latency by which it is normally preceded have been studied in conditions where the level of phosphorylase a was greatly modified by the addition of either the pure enzyme or of antibodies directed against it. In the presence of liver or muscle phorphorylase a, glycogen synthetase phosphatase was nearly inactive; phosphorylase b had only a slight effect. Antibodies, obtained in the rabbit against dog liver phosphorylase, strongly depressed the activity of phosphorylase a in a mouse liver preparation; they simultaneously allowed an immediated activation of glycogen synthetase.These results indicate that the lag period that precedes that activation of glycogen synthetase in a liver filtrate is the time required for the conversion of phosphorylase a into b by phosphorylase phosphatase. The previously reported shortening of the lag period by glucose, caffeine and nicotinamide or by a tratment with glucocorticoids is entirely explained by the faster inactivation of phosphorylase in the same conditions. The elongation of the lag period by glycogen and its supporession by AMP and magnesium remained however to be explained. It has been shown that the dose of glycogen that prolongs the lag period also inhibits phosphorylase posphatase, wherease AMP and magnesium counteract the inhibition of synthetase phosphatase by phosphorylase a.
Antigenic Properties of Bacillus licheniformis Cell Wall Components
Authors: Hughes R. Colin , Thurman Paul F. , Salaman Myer R. 
Published: March 2005

Antibodies directed against mucopeptide were obtained by immunization of rabbits with Bacillus licheniformis N. C. T. C. 6346 cell walls extracted chemically to remove the teichoic acids. The teichuronic acid component present in whole walls or alkali extracted walls of the organism was not significantly immunogenic in rabbits. The mucopeptide antisera reacted strongly with sonicates of Bacillus licheniformis and Bacillus subtilis mucopeptides and the homologous reaction was inhibited by soluble fragments of low molecular weight derived from mucopeptide. The best inhibition of the homologous reaction was obtained with fragments containing peptide and hexosamine material isolated from the soluble products of lysozyme treatment of Bacillus licheniformis mucopeptide.Immune sera obtained from rabbits immunized with intact Bacillus licheniformis N. C. T. C. 6346 walls containing mucopeptide, teichuronic acid and teichoic acids contained antibodies directed mainly against the teichoic acids. The immune response to the mucopeptide component was greatly reduced compared to that obtained when wall preparations lacking teichoic acids were used as immunizing antigens.
Studies on Hog Intestine Mucosa Peroxidase
Authors: StelmaszyŃSKA Teresa , ZgliczyŃSKI Jan M. 
Published: March 2005

A method has been developed for isolating and purifying peroxidase from hog intestinal mucosa. The enzyme exhibits an absorbance ratio A417 nm/A280 nm of 0.906.Studies on the homogeneity of intestinal peroxidase by electrophoresis on polyacrylamide gel and cellulose acetate strips showed its high degree of purification; the enzyme showed a single band at pH 8.45 with the cathodic mobility.Intestinal peroxidase is a haemoprotein. Its absorption spectrum, as well as that of its derivatives (CN‐peroxidase, reduced peroxidase, CN‐reduced peroxidase and pyridine haemochromogen) is of the same type as the spectrum of lactoperoxidase and its corresponding derivatives.Kinetic studies on the reaction of intestinal peroxidase with hydrogen peroxide and guaiacol showed that this haemoprotein has the properties of true peroxidase (donor: H2O2 oxidoreductase). The k1 value was determined as 5.9 × 106 M−1× sec−1, and Km (H2O2) was 260 μM. Optimum pH of the studied peroxidase was in the range pH 7.5–8.Intestinal peroxidase, with respect to deamination and decarboxylation of amino acids, does not resemble the myeloperoxidase.
The Regulative Properties of UDPglucose: d‐Fructose‐6‐phosphate 2‐Glucosyltransferase (Sucrose Phosphate Synthetase) from Vicia faba Cotyledons
Authors: DE Fekete Maria A. R. 
Published: March 2005

Sucrose phosphate synthetase of cotyledons of Vicia faba was purified about 130‐fold by means of ammonium sulfate and protamine fractionation. After freezing and thawing an activator could be separated by centrifugation from the purified enzyme. The regulatory properties of the activator‐bound and activator‐devoid enzyme were compared. Under the normal conditions of assay the activator‐devoid enzyme had scarcely any activity, but could be activated by citrate, a number of dicarboxylic acids and protamin. The saturation curves of these effectors were sigmoidal. Also the substrate saturation curves were sigmoid shaped in absence of activator but the presence of activator converted them to a hyperbolic form.Quite different was the effect of citrate on the activity of the activator‐bound enzyme: at low concentration it inhibited the production of sucrose‐6‐phosphate. At 10–20 mM citrate a minimum of activity could be measured. At higher citrate concentrations a reactivation occurred. This activator‐bound preparation could be further inhibited, but not reactivated, by UDP, UTP, ATP, ADP and other phosphates which had scarcely any influence on the activity of the activator‐devoid enzyme. Experiences where the influence of citrate concentration was investigated on the UTP‐inhibited enzyme suggest that both effectors share binding sites.The role of citrate in the control of the activities of sucrose phosphate synthetase (activation) and phosphofructokinase (inhibition), both enzymes competing for the branchpoint metabolite fructose‐6‐phosphate, is discussed.
Effects of Benzimidazole on the Oxygen‐Induced Biosynthesis of Hemoproteins in Yeast
Authors: Sels André A. , Verhulst Anne‐Marie 
Published: March 2005

Benzimidazole almost completely inhibited respiratory adaptation of yeast under conditions where total protein synthesis was only partially inhibited.
The effects of benzimidazole on the synthesis of individual hemoproteins were examined. The production of enzymatically active cytochrome oxidase was almost totally blocked; this accounts for the interruption of respiratory adaptation. The biosynthesis of the NADH (and succinate): cytochrome c oxidoreductase segments, which include the cytochromes b and c1, was only partially inhibited. The induced synthesis of iso‐1‐cytochrome c displayed a singular insensitivity to the action of the drug. The mechanism of inhibition by benzimidazole appears to be different from that of cycloheximide and chloramphenicol.
The Effect of Alkylation on Substrate‐ and Effector‐Binding Sites in Pigeon Liver NAD Kinase
Authors: Apps David K. 
Published: March 2005

At pH 7.5, inactivation of NAD kinase by bromoacetyl pyridine occurs in three independent pseudo‐first‐order stages.
Below pH 7.5, only two stages are distinguishable.
The final stage alkylation leads to total inactivation, the earlier stages to the formation of an enzyme species with modified properties.
Effects of pH on the time courses of inactivation suggest that the first stage may involve a variable number of sulphydryl groups.
The final stage probably involves alkylation of a sulphydryl, with abolition of NAD binding.
No central role in catalysis can be postulated for any of the groups modified by bromoacetyl pyridine; two groups known to participate in catalysis and the binding of ATP · Mg are apparently not alkylated.
Inhibition by L‐malate and by free ATP may occur by attachment of these effectors at separate modifier sites.
Studies on the Protein Moiety of Endotoxin from Gram‐Negative Bacteria
Authors: Wober Wolfgang , AlaupoviĆ Petar 
Published: March 2005

Conjugated protein isolated from the endotoxin complex of Serratia marcescens 08 by 1% acetic acid hydrolysis was characterized by analytical ultracentrifugation, electrophoretic and immunological properties and chemical analysis. The chemical composition of conjugated protein and other degraded fragments of endotoxin showed that all characteristic constituents of lipid A were present exclusively in conjugated protein. Successive treatment of conjugated protein with trypsin and pronase resulted in the isolation of corresponding tryptic and pronase cores which were characterized by an increased content of lipid A constituents. Lipid A was separated as an entity from the conjugated protein only after hydrolysis with 0.1 N hydrochloric acid. This result confirms our previous proposal that lipid A is covalently linked to the protein moiety in whole endotoxin of S. marcescens 08. “Conjugated” protein isolated by acetic acid hydrolysis and “simple” protein prepared by hot aqueous phenol treatment of whole endotoxin differ from one another not by the presence or absence of lipid A but rather by the presence of the entire lipid A moiety in the conjugated protein and only a fragment of lipid A in the simple protein.Conjugated protein and its tryptic and pronase cores were immunogenic and possessed a common antigenic determinant with simple protein and its corresponding cores. Toxicity studies revealed that both conjugated and simple proteins retained to different degrees the toxic properties of whole endotoxin. Sodium dodecyl sulfate had an enhancing rather than diminishing effect on the toxicity of endotoxin and its various fragments. The importance of lipid A as the toxic factor of endotoxins was established not only indirectly by determining the toxicity of each fragment containing lipid A, but also directly by demonstrating that lipid A dispersed in a Tris‐dodecyl sulfate buffer displayed toxic properties similar to those of the lipopolysaccharide preparation.
Acid Soluble Calf Skin Collagen
Authors: Rauterberg Jürgen , Kühn Klaus 
Published: March 2005

The α1‐chain of acid soluble calf skin collagen was cleaved with cyanogen bromide, and the resulting peptides were separated by ion exchange and molecular sieve chromatography. Eight different peptides could be isolated as expected from the seven methionyl residues of the chain. Their size was determined by gel filtration, dodecyl sulfate disc electrophoresis, measurement of electron micrographs of renatured peptides, and amino acid analysis. Peptides, differing in length between 19 and 270 residues were found. The C‐terminal peptide α1‐CB6 occurred in two variants (CB6a and CB6b), differing in size, chromatographic behaviour and amino acid composition. The results suggest that CB6a contains about 15 amino acid residues more than CB6b.The amino acid compositions of the peptides were in good agreement with the composition of the α1‐chain. All CNBr‐peptides, including the sum of CB6a and CB6b, were isolated in approximately equimolar amounts, thus excluding the possibility of repeating sequences within the chain. The order of the CNBr‐peptides was established by electron microscopy and by comparative amino acid analysis of overlapping collagenase derived peptides and uncleaved CNBr‐peptides. It was found to be the same as in α1 from rat skin collagen.
Nitrogen Fixation by Extracts of Mycobacterium flavum 301
Authors: Biggins David R. , Postgate John R. 
Published: March 2005

Crude extracts of lactate‐grown Mycobacterium flavum 301 reduced acetylene to ethylene with NADH as electron donor provided benzyl viologen was present; ATP was required. Lactate, pyruvate, H2 or glucose‐6‐phosphate were also active donors via appropriate dehydrogenases.
Crude extracts also reduced cyanide to methane with NADH, ATP and benzyl viologen.
Debris (composed of wall and membrane fragments) had lactic, pyruvic and NADH dehydrogenase activities. They reduced acetylene with sodium dithionite or NADH. Benzyl viologen was not required with NADH; ATP and O2 inhibited the reaction.
Crude extracts were as sensitive to inactivation by oxygen as extracts from anaerobic bacteria. Glutathione decreased and ATP increased oxygen‐sensitivity.
Debris preparations were not inactivated by oxygen.
These results suggest that the nitrogen‐fixing system of M. flavum 301 resembles those of other aerobes, but that its mechanisms for protecting nitrogenase from oxygen are more primitive.
Partial Enzymic Digestion of 50 S Ribosomal Subunits from Escherichia coli
Authors: Spencer Margaret E. , Walker Ian O. 
Published: March 2005

50 S ribosomal subunits from Escherichia coli were incubated with an endonuclease specific for single‐stranded nucleic acid. After incubation the sedimentation coefficient remained unaltered but gel filtration showed that 10% of the nucleic acid in the ribosome had been degraded to small fragments. When the enzyme‐treated native subunits were subsequently unfolded in EDTA their sedimentation properties were similar to controls. Thermal denaturation in the presence of formaldehyde produced small fragments of RNA with a sedimentation coefficient of 2 S.Subunits which had first been unfolded in EDTA and then incubated with enzyme were rapidly degraded to small fragments with a sedimentation coefficient of 2 S. The degraded fragments had 20% hyperchromism on thermal denaturation which showed that the secondary structure of the RNA had remained intact. These experiments were interpreted in terms of the hairpin‐loop model of RNA. They show that on the surface of the native subunit there is no interhelical single‐stranded RNA which is accessible to enzyme whereas there is a significant amount of intrahelical single‐stranded RNA. In the unfolded subunit the interhelical regions become exposed to attack by the enzyme.A digest of unfolded subunits was separated by gel filtration on Sephadex G‐100 into three fractions. Fraction I, which eluted at the exclusion volume of the column, was mainly aggregated protein. Fraction II, which contained 65% of the ultraviolet absorbing material and no protein, was hyperchromic and the circular dichroic spectrum was consistent with this fraction having double‐helical secondary structure. Fraction II moved as a single, sharp boundary on sedimenta‐tion with s20= 1.7 S and had a molecular weight of 15700. Fraction III, which contained 35% of the ultraviolet absorbing material and no protein, was low molecular weight nucleotide with no secondary structure.
Structure of Phycocyanobilin
Authors: Schram Bernard L. , Kroes Hanno H. 
Published: March 2005

The structure of phycocyanobilin, the prosthetic group of phycocyanin, has been investigated by means of mass spectral, infrared, and nuclear magnetic resonance studies. The linear tetrapyrrolic compound has a molecular weight of 588 and contains an intramolecular hydrogen bond, the rupture of which forms the basis for several of the chemical transformations. Esterification, for example, is accompanied by dehydrogenation, so the molecular weight of the dimethyl ester is 614.The structure of the phycobilin P 655 has been deduced from an analysis of the properties of phycocyanobilin; this structure is nearly identical to the one proposed by Cole, Chapman, and Siegelman. For the phycobilin P 608 only a tentative structure can be presented.
The Respiratory System of Azotobacter vinelandii
Authors: Ackrell Brian A. C. , Jones Colin W. 
Published: March 2005

A detailed procedure is described for the isolation of stable respiratory membranes of relatively high phosphorylation efficiency from nitrogen‐fixing cultures of Azotobacter vinelandii (P/O, NADH = 0.90–1.10).
Three phosphorylation sites are detectable. These are located at the level of NADH dehydrogenase (Site I; P/2e 0.45), between the primary dehydrogenases and the cytochromes (Site II; P/2e 0.53) and on the minor terminal pathway, to the oxygen side of the c‐type cytochromes (Site III; P/2e 0.22).
Switching of electron flow between the terminal oxidation pathways with low concentrations of KCN and 2‐n‐alkyl‐4‐hydroxyquinoline‐N‐oxide causes changes in oxygen uptake and phosphate esterification which are compatible with the postulated locations of the three phosphorylation sites and which demonstrate, indirectly, the non‐phosphorylating nature of the b1→a2 major terminal pathway.
Phosphorylation efficiences with ascorbate plus purified A. vinelandii cytochromes c4 and c5, horse heart cytochrome c and the artificial electron electron mediators 2,6‐dichlorophenol indophenol and N,N,N′,N′‐tetramethyl‐p‐phenylene diamine indicate that the minor terminal pathway is further split into a slow, phosphorylating pathway (c5→oxygen) and a faster, non‐phosphorylating pathway (c4→oxygen).
Turnover of the Deoxyribonucleoside Triphosphates in Escherichia coli 15 T during Thymine Starvation
Authors: Neuhard Jan , Thomassen Elisabeth 
Published: March 2005

Since hydroxyurea specifically inhibits the biosynthesis of deoxyribonucleotides in Escherichia coli, analysis of the deoxyribonucleoside triphosphate pools following hydroxyurea addition makes possible a determination of the turnover of these compounds in vivo. This method has been used in the present work to study the effect of thymine starvation of E. coli 15 T on the turnover of dGTP, dATP, and dCTP. From the results obtained the following conclusions may be made.In exponentially growing cultures DNA synthesis can account for the entire turnover of the deoxyribonucleoside triphosphates.Removal of thymine from the growth medium results in the appearance of catabolic reactions that degrade dATP and dCTP. During the first 20 min of thymine starvation the rates of degradation of dATP and dCTP are of the same magnitude as those accounted for by DNA polymerization during exponential growth. After 75 min, however, the decay rate of dCTP has increased 5‐fold while the rate of dATP decay remains constant. During the entire period of thymine starvation the rate of decay of dGTP is very low, i.e. one sixth of that observed during exponential growth.The end products of the catabolic reactions involved are to a large extent excreted into the growth medium as diphenylamine‐reacting material.By determining the rate of accumulation of the individual deoxyribonucleoside triphosphates following thymine deprivation, and adding these values to the decay rates, determined in the presence of hydroxyurea, it is possible to estimate the endogenous rate of synthesis of dGTP, dATP and dCTP under these conditions. The results show that removal of thymine from E. coli 15 T results in a significant reduction in the rate of dGTP synthesis, essentially no effect on the rate of dATP synthesis, and an increasing rate of dCTP synthesis reaching 6‐fold values after 75 min of starvation.
Isolation and Characterization of Seryl‐tRNA Synthetase from Yeast
Authors: Heider Henning , Gottschalk Ellen , Cramer Friedrich 
Published: March 2005

A novel method for the isolation in 29% overall yield of seryl‐tRNA synthetase from baker's yeast is described. The method includes opening of the cells by autolysis with toluene, two ammonium sulfate fractionations, a combined RNAase and DNAase digestion of the nucleic acid components and successive chromatographic fractionations on phosphocellulose and DEAE‐cellulose. The enzyme shows an unusual affinity for phosphocellulose.The purified enzyme is homogeneous by equilibrium ultracentrifugation, by disc electrophoresis and by dodecylsulfate gel electrophoresis. The enzyme consists of two subunits, the molecular weight of which in the denatured and native states is 60 000 and 61 000, respectively, as determined by ultracentrifugation and dodecylsulfate gel electrophoresis. The total enzyme dissociates easily into the subunits, even in dilute buffer solution. The molecular weight of the total enzyme was determined by ultracentrifuge measurements to be 115000. Even under these conditions at lower concentration the enzyme tends to dissociate; the data point to an active dimer of molecular weight 120 000.No free N‐terminal amino acid could be found. The enzyme was further characterized by determination of its ultraviolet spectrum and content of tryptophan and tyrosine.
Diacetyl (Acetoin) Reductase from Aerobacter aerogenes
Authors: Hetland Øyvind , Olsen Bjørn R. , Christensen Terje B. , Størmer Fredrik C. 
Published: March 2005

The native and subunit molecular weights of diacetyl (acetoin) reductase from Aerobacter aerogenes have been investigated by sedimentation equilibrium analysis and gel electrophoresis. The values obtained are 100000 for the native enzyme and 25000 for the subunit. The native enzyme is dissociated into four equal‐sized subunits by exposure to guanidine hydrochloride, urea, or dodecylsulfate. The subunits can reassociate in the presence of bovine serum albumin to yield the native enzyme.Electron micrographs of enzyme molecules, negatively stained, show that they appear primarily as tetramers with four subunits at the corners of squares. The molecular weight as calculated from the diameter of the subunits is consistent with the values obtained by sedimentation equilibrium and gel electrophoresis.
Deoxyribonucleotide Phosphatase from Rat Liver and Cultured Mouse Fibroblasts
Authors: Magnusson Göran 
Published: March 2005

An enzyme which catalyzes the preferential dephosphorylation of the 5′‐phosphates of deoxythymidine, deoxyuridine and deoxyguanosine was purified 100‐fold from rat liver. The preparation appeared to be free from contaminating phosphatase activities. The dephosphorylation of deoxyribonucleotides was dependent on the presence of Mg2+ ions and had a pH optimum around 6.0. The Km value for the dephosphorylation of deoxythymidine 5′‐phosphate was 5.7 mM.High activities of the enzyme were found in cultured mouse fibroblasts. In parasynchronously growing cells no changes of enzyme activity were found during the cell cycle.
The Thiol Groups of Rat Liver Cystathionase
Authors: Dème Danielle , Durieu‐trautmann Odile , Chatagner Fernande 
Published: March 2005

Rat liver cystathionase (homoserine hydrolyase) catalyzes the deamination of homoserine and the desulfhydration of cysteine. A study has been made of the SH groups of the highly purified enzyme. The titration of the SH groups by p‐chloromercuribenzoate and 5,5′‐dithiobis‐(2‐nitrobenzoic acid) indicated that the enzyme contains approximatively 12 SH per mole (mol. wt. 170000) of native enzyme and 20 SH per mole of urea‐denaturated enzyme.On the basis of their reactivity towards SH reagents the SH groups of cystathionase have been classified into 4 classes.Addition of pyridoxal phosphate, the coenzyme of cystathionase, prior to treatment with SH reagents did not modify the availability of SH groups for SH reagents; however, addition of homoserine, a substrate for cystathionase, or of l‐alanine, a competitive inhibitor for both homoserine deamination and cysteine desulfhydration, led to a striking protection of several SH groups, 4 and 8, respectively.The over‐all results are discussed in relation to the hypothesis of a “double” active center composed of one site necessary to the binding of homoserine and one other involved in the binding of cysteine. In addition the hypothesis that cystathionase may consist of subunits is considered, taking into account the symmetry of the SH groups in each class and the number of pyridoxal phosphate binding sites on the protein.
Imidazole Group‐Catalyzed Reactions in Formaldehyde
Authors: Martin Charles J. , Oza Narenda B. , Marini Mario A. 
Published: March 2005

The catalysis of p‐nitrophenyl acetate hydrolysis by imidazole compounds in formaldehyde solution occurs at a rate lower than in water.
Kinetically determined pK' values of imidazole and its derivatives agree with titrimetric values and the catalytically active species is the free base form of the N‐hydroxymethyl adduct of the imidazole ring.
With imidazole as catalyst in formaldehyde, N‐acetyl‐N′‐hydroxymethylimidazolium cation is apparently a short‐lived intermediate in the reaction. The hydroxymethyl adduct, although removable by dilution, is not displaced by substrate during catalysis.
These results provide additional support for the occurrence of a reaction between for‐aldehyde and the imidazole ring and its kinetic consequences parallel those seen in the effect of formaldehyde on chymotrypsin‐catalyzed reactions.