bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self‐Oscillations in Glycolysis 1. A Simple Kinetic Model
Authors: SEL'KOV E. E. 
Published: March 2005

The paper describes a simple kinetic model of an open monosubstrate enzyme reaction with substrate inhibition and product activation. A comparison between the model and the phosphofructokinase reaction shows a close resemblance between their dynamical properties. This makes it possible to explain qualitatively most experimental data on single‐frequency oscillations in glycolysis. A mathematical analysis of the model has shown the following.

In the model, at a definite relationship between the parameters, self‐oscillations arise.
The condition of self‐excitation is satisfied more readily with a lower source rate, larger product sink rate constants, lower product‐enzyme affinity and higher enzyme activity.
Self‐oscillations exist only in a certain range of values of the parameter determining the degree of substrate inhibition. This range increases with decreasing source rate. Too strong or, conversely, too weak substrate inhibition leads to damped oscillations.
The period of self‐oscillations depends on the degree of substrate inhibition, the source rate, the sink rate constant, the enzyme activity, the affinity of the substrate and the product for the enzyme; it decreases with an increase in these values.
With an increase in the relative sink rate constant the steady state amplitude of self‐oscillations initially increases until a definite maximum is reached and then drops to zero.
A self‐oscillatory state in the phosphofructokinase reaction exists only when the maximum rate of this reaction is essentially higher than the source rate, and lower than the maximum rate of the reactions controlling the sink of the products.
An experimental investigation of self‐oscillations in the phosphofructokinase reaction may be considerably simplified by using a reconstituted system consisting of a small number of reactions with an irreversible sink of the products and artificial substrate supply. In this case the above relationship (section 6) should hold.
Nouvelle méthode de purification des polypeptide synthétases VII
Authors: FISCHER‐FERRARO C. , BELJANSKI M. 
Published: March 2005

A new method for purification of “polypeptide synthetase” from Alcaligenes faecalis is described in which nucleic acids are removed by purification on DEAE‐cellulose with a recovery of 60–75% of the initial enzymatic activity.The enzyme preparation catalyses the binding of the naturally occuring l‐amino acids to a messenger‐like RNA whose properties have been previously described. The reaction requires the addition of any one of the four nucleoside triphosphates (ATP, GTP, CTP or UTP), which is degraded to the corresponding nucleoside diphosphate and orthophosphate. For certain amino acids, however, the requirement for a nucleoside triphosphate is limited to two of the four.The purified enzyme preparation, unlike crude extracts, does not catalyse an amino dependent ATP‐[32P]PPi exchange. Neither crude extracts, nor purified preparations show detectable exchange between [32P]PPi and GTP, CTP, or UTP in the presence or in the absence of l‐amino acids.The presence of more than one enzyme in the purified preparation was demonstrated by further substantial fractionation of [14C]leucine binding activity and separation of this from [14C]alanine binding activity. However, no fractionation, which was dependent on a specific nucleoside triphosphate, could be achieved.
Biochemical Studies on Lipopolysaccharides of Salmonella R Mutants
Authors: DRÖGE W. , LÜDERITZ O. , WESTPHAL O. 
Published: March 2005

From Salmonella R lipopolysaccharides of the chemotypes Rc, Rd1, and Rd2 oligosaccharides were prepared and their structure studied by the following methods: quantitative sugar analyses; periodate oxidation followed by borohydride reduction in order to transform the l‐glycero‐d‐mannose residues into d‐mannose residues; methylation of original and transformed oligosaccharides, methanolysis and gas chromatographic identification of the methylated heptoses or mannoses; the action of glycosidases; serological tests. The results of the study are in agreement with the formulae given below for the different oligosaccharides. The anomeric form of the glucose unit linked to heptose, as well as that part of the oligosaccharides which contains the 2‐keto‐3‐deoxy‐octonate residues [KDO] remain uncertain.Chemotypes Rd2: Heptose pα 1→[KDO]x; Rd1: Heptose pα 1→3 Heptose pα 1→[KDO]x; Re: Glucose 1→3 Heptose pα 1→3 Heptose pα 1→[KDO]x.
Biochemical Studies on Lipopolysaccharides of Salmonella R Mutants
Authors: MÜHLRADT P. , RISSE H. J. , LÜDERITZ O. , WESTPHAL O. 
Published: March 2005

In an in vitro system, containing 20,000 ×g cell wall particles and 100,000 ×g cell sap supernatant of various Salmonella rough mutants the rate of galactose transfer from UDP‐[14C]‐galactose to the core lipopolysaccharide was studied and the following results obtained:

Cell wall partieles from the S. minnesota mutants mR5, mR7, and mR8 are poor acceptors for galactose. The lipopolysaccharides of these mutants contain heptose and phosphate in a molar ratio of 2:2, whereas in normal lipopolysaccharide of Salmonella the ratio is 2:3.
20,000 ×g cell wall fractions from mutants which produce lipopolysaccharide of normal phosphate content, such as those from S. minnesota mRz or S. typhimurium tmM are good acceptors for galactose.
Phosphate‐poor cell wall particles can be treated with ATP and enzyme extracts of mutants containing lipopolysaccharide of normal phosphate content to yield proper acceptors for galactose.
A radioactive disaccharide which chromatographically behaves like melibiose, and which after treatment with α‐galactosidase yields [14C]galactose can be isolated from partial hydrolysates of cell wall particles which have previously been incubated with UDP‐[14C]galactose and enzyme extract from tmM. This result is the same whether phosphate is already present in the cell wall fraction or is introduced enzymatically by the addition of ATP to the incubation mixture.

It is concluded that mR5 and mR8 are defective in a lipopolysaccharide phosphorylating enzyme and that lack of phosphate groups in the lipopolysaccharide results in an incomplete core because unphosphorylated lipopolysaccharide acts only as a poor acceptor in the galactose transfer reaction.
Enzymatic Inactivation of Glutamine Synthetase in Enterobacteriaceae
Authors: GANCEDO C. , HOLZER H. 
Published: March 2005

The inactivation of glutamine synthetase in vivo on addition of ammonium ions to the culture medium was studied in different microorganisms. Only those belonging to the family of Enterobacterioceae showed inactivation. The transfer activity of the enzyme was much less affected than the synthetic one. As in Escherichia coli, the glutamine synthetase of Salmonella typhimurium could be inactivated in vitro in a system requiring glutamine, ATP, Mg2+ and an enzyme.The inactivating enzymes of E. coli and S. typhimurium have been separated and cross‐tested against their synthetases. The inactivating enzymes inactivated both glutamine synthetases in the in vitro inactivation process. In contrast, synthetases of microorganisms which did not exhibit in vivo inactivation were not affected by these inactivating enzymes.The fact that only glutamine synthetases of Enterobacteriaceae could be inactivated suggests that this regulatory mechanism is limited to a group of organisms possibly derived from the same ancestor.
Soybean Lipoxygenase
Authors: ALLEN J. C. 
Published: March 2005

The reliability of the assay of lipoxygenase has been improved by minimising sources of error, such as the adherence of the enzyme to the glass of the containing vessel.
The electrophoretic method of preparing crystalline lipoxygenase has been improved, and a new chromatographic purification has been developed.
The shape of the pH‐activity profile of the enzyme has been shown to depend critically upon the amount of organic solvent present in the solution, as well as upon its ionic strength. These effects are discussed, and an attempt has been made to fit theoretical curves to the pH‐profiles in solutions containing no organic solvents. The dissociation constants for the ionisable groups on the enzyme extracted from these data are pKa= 6.5‐6.8 and pKb= 9.0‐9.1, in 0.2 M Tris.
Micelle formation has little effect on the Km of the enzyme. However, substrate concentration vs. activity curves show perturbations at the critical miselle concentration in certain instances, and a possible relationship between the critical micelle concentration and a substrate concentration derived by extrapolation of the activity curves is presented.
Studies on Methionyl Transfer RNA Synthetase
Authors: LEMOINE F. , WALLER J.‐P. , van RAPENBUSCH R. 
Published: March 2005

Methionyl transferRNA (tRNA) synthetase fromEscherichia colistrain K‐12 was purified 675 fold from extracts of kilogram quantities of cell paste as a product that appears to be homogenous on chromatography, electrophoresis and ultracentrifugation. The activities measured by the ATP‐PPi exchange assay and by methionyl tRNA formation did not vary significantly during the purification. The final product, which catalyzed the exchange of 1,000 μmoles of pyrophosphate into ATP/mg protein in 15 min at 37°, was obtained with a yield of 50%.Some general properties of purified methionyl tRNA synthetase are described. The enzyme has a sedimentation coefficient (s20,w) of 6.5 S, and a molecular weight of 173,000. In the presence of dissociating reagents (8M urea or 6M guanidine) it undergoes dissociation into subunits which have a molecular weight of about 43,000. Within the limits of the accuracy of the ultracentrifugation analyses, there was no indication of heterogeneity in mass among these subunits. Furthermore, acrylamide gel electrophoresis in the presence of 8 M urea failed to reveal any significant heterogeneity of the dissociated enzyme. The results indicate that methionyl tRNA synthetase fromE. coliK‐12 is composed of four, possibly identical, subunits.
The Influence of Thyroid Hormones on β‐Hydroxy‐β‐Methylglutaryl‐Coenzyme A Reductase of Rat Liver
Authors: GUDER W. , NOLTE I. , WIELAND O. 
Published: March 2005

Rat liver β‐hydroxy‐β‐methylglutaryl‐CoA reductase has been measured by an isotopic assay system. In normal rats, an activity of about 70 nmoles/g liver · hour was found.Thyroidectomy lowers this rate to less than 50%. Injection of 3,3′,5′‐tri‐iodothyronine into hypothyroid rats brings the activity up to the range of normal animals after a latent period of about 30 hours.
Studies on the Metabolism of C19‐Steroids in Rat Liver
Authors: LISBOA B. P. , GUSTAFSSON J.‐Å. , SJÖVALL J. 
Published: March 2005

The formation of polar C19‐steroids with a 3‐oxo‐Δ4‐structure after incubation of testosterone with 105,000 ×g microsomes of adult male rat liver was investigated. The ultraviolet‐positive metabolites were isolated by thin‐layer chromatography. The isolated compounds were identified as 2β‐, 6β‐, 7α‐, and 16α‐hydroxytestosterone by means of gas‐liquid chromatography‐mass spectrometry.A dihydroxytesterone was also isolated and tentatively identified as 6β,16α,17β‐tri‐hydroxyandrost‐4‐en‐3‐one.
Properties of Aqueous Dispersions of Phospholipid and Cholesterol
Authors: BRUCKDORFER K. R. , EDWARDS P. A. , GREEN C. 
Published: March 2005

Very little lipid can be extracted with diethyl ether or chloroform from aqueous dispersions of phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid, or from mixed dispersions of phosphatidic acid and phosphatidylethanolamine with cholesterol. Nearly all of the cholesterol and about 60% of the phosphatidylcholine can be removed from a dispersion of these two lipids in equimolar proportions but not from a dispersion of two molecules of phosphatidylcholine to one molécule of cholesterol.
NaCl and CaCl2 greatly increase the extraction of lipids from phosphatidylcholine and phosphatidylcholine/cholesterol dispersions whereas urea and dimethylsulphoxide prevent extraction.
Cholesterol molecules readily exchange between rat erythrocytes and dispersions of equimolar proportions of phosphatidylcholine and cholesterol.
At lower proportions of cholesterol, the dispersions remove cholesterol from the ghosts. Up to 60% of the sterol can be removed from the ghost membrane.
Phosphatidylcholine/cholesterol dispersions are readily attacked by phospholipase D in the absence of ether but dispersions of phosphatidylcholine alone need ether present to facilitate enzymic attack.
These properties are compared with those of soluble and structural lipoproteins.
The Incorporation of Steroid Molecules into Lecithin Sols, β‐Lipoproteins and Cellular Membranes
Authors: BRUCKDORFER K. R. , GRAHAM J. M. , GREEN C. 
Published: March 2005

The dispersion of various steroids in aqueous solution with ovolecithin was investigated and the following molar ratios of lecithin to steroid obtained: cholesterol, 1:1; 7‐dehydrocholesterol, 13.3:1; ergosterol, 13.1:1; sitosterol, 2.0:1; sterophenol 4.2:1; cholesta‐4,6‐dien‐3‐one, 2.0:1; cholest‐4‐en‐3‐one, 1.7:1.
The cholesterol contents of sterol‐depleted cellular membranes can be restored to their original level by incubation with plasma or an equimolar dispersion of cholesterol and ovolecithin, in the presence of 10% dimethylsulphoxide (v/v).
Cholesta‐4,6‐dien‐3‐one, cholest‐4‐en‐3‐one, 7‐dehydrocholesterol and sterophenol can exchange readily with the cholesterol erythrocyte ghosts and can replace cholesterol molecules removed from the membrane. Ergosterol can do so only to a very limited extent.
7‐Dehydrocholesterol exchanges between rat erythrocyte ghosts and human piasma β‐lipo‐proteins in the same way as cholesterol. Cholesta‐4, 6‐dien‐3‐one and cholest‐4‐en‐3‐one also exchange but, in addition, there is a net uptake of these steroids by β‐lipoproteins. The extra steroid entering the lipoproteins is probably dissolved in the hydrophobic core of the latter.
The exchange of cholesta‐4,6‐dien‐3‐one between erythocyte ghosts and lecithin/steroid dispersions or β‐lipoproteins is much more rapid than that of cholesterol. The rate of exchange of the dienone, like that of cholesterol, is increased by the addition of a small quantity of dismethylsulphoxide to the medium.
On Collagens of Invertebrates with Special Reference to Mytilus edulis
Authors: PIKKARAINEN J. , RANTANEN J. , VASTAMÄKI M. , LAMPLIAHO K. , KARI A. , KULONEN E. 
Published: March 2005

The amino acid compositions of Metridium‐, Lumbricus‐ and Mytilus‐collagens corresponded to those of the lowest vertebrates: the content of imino acids was low and that of serine and threonine high. Metridium‐collagen also contained cystine and large amounts of hydroxylysine. In Lumbricus‐collagen the hydroxylation of proline was almost complete and the total content of hydroxy amino acids thus exceptionally high.The solubility of collagens from the invertebrates varied in wide range. In some cases, e. g. the byssus apparatus of Mytilus, the insolubility seems to depend on the stabilizing effect of the adjacent materials which is manifested also in the unique thermal shrinking temperature of 90°.The starch‐gel electrophoretic patterns were studied on soluble collagens from the following species: octopus, Loligo, Lumbricus, Diphyllobothrium, Mytilus, and Metridium. A single α‐component pattern, resembling that from lamprey, was observed in all the cases.
Incorporation of Choline into the Outer and Inner Membranes of Isolated Rat Liver Mitochondria
Authors: KAISER W. , BYGRAVE F. L. 
Published: March 2005

Separation of the inner and outer membranes following incubation of mitochondria with 14C‐labelled choline chloride revealed the specific radioactivity both per mg protein and per μg phospholipid phosphorus to be greater in the outer membrane. Under the present conditions of incubation, the incorporation into the microsome fraction was less than 10% (on a mg protein basis) of that into the isolated mitochondria.Labelled choline is also incorporated into the membrane components of isolated mitochondrial fractions, but to a lesser extent than that incorporated into the membranes of intact mitochondria, and in different proportions.The phospholipid phosphorus contents of the “pure” outer and “pure” inner membranes of isolated rat liver mitochondria are respectively about 18.3 and 6.1 μg phosphorus per mg protein.The data are discussed with particular refernce to the biosynthesis of the mitochondrial membranes and to the biogenesis of mitochondria.
2‐Amino‐2, 6‐Dideoxy‐L‐Mannose (L‐Rhamnosamine) Isolated from the Lipopolysaccharide of Escherichia coli 03: K2ab(L):H2
Authors: Jaan B. , Jann K. 
Published: March 2005

From the lipopolysaccharide of Escherichia coli U41/14 (serotype 03:K2ab(L):H2) an unusual amino sugar was isolated.By sequential oxidation with periodate and hypoiodite and by oxidation with periodate, followed by detection of acetaldehyde formed, the amino sugar was characterized as a 2‐amino‐dideoxyaldose.The hydrochloride of the amino sugar, in comparison to those of 2‐amino‐2,6‐dideoxy‐D‐glucose, 2‐amino‐2,6‐dideoxy‐L‐galactose, 2‐amino‐2,6‐dideoxy‐D‐mannose, 2‐amino‐2,6‐dideoxy‐D‐allose, and 2‐amino‐2,6‐dideoxy‐D‐gluose, was studied with aid of ion exchange column chromatography. The N‐acetylated amino sugar was compared with the N‐acetylated reference amino sugars with regard to their relative mobilities in paper chromatography. The amino sugar alcohols and reference amino sugar alcohols were studied using paper electrophoresis in molybdate buffer.On the basis of the results obtained the unknown amino sugar was identified as 2‐amino‐2,6‐dideoxymannose (rhamnosamine). Its optical rotation showed it to be of the L‐configuration.This is the first report on the natural occurrence of L‐rhamnosamine.
Some Properties of Lysyl Ribonucleic Acid Synthetase from Escherichia coli
Authors: Waldenström J. 
Published: March 2005

When the lysyl‐RNA synthetase from Escherichia coli was incubated with ATP and L‐lysine in the presence of Mg++, a complex of lysyl‐RNA synthetase, AMP and lysine was formed. The complex was isolated by filtration on Sephadex G‐25. Maximum complex formation was obtained at a molar ratio of substrate to enzyme between 3 and 4. The complex was very stable at low temperatures in the absence of Mg++, while incubation at 45° for 10 minutes gave 75% breakdown of the complex. The amino acid of the complex could be transferred to transferRNA in a reversible reaction that did not require Mg++. The transfer reaction was enhanced by the monovalent cations NH4+, Na+, and K+.The lysyl‐RNA synthetase from E. coli recognized about 70% of the lysine specific chains of yeast transferRNA, while the yeast enzyme recognized about 80% of the lysine specific chains of E. coli transferRNA. The esterification of E. coli transferRNA by the yeast enzyme proceeded at only 2% of the rate obtained with homologous transferRNA, while the E. coli enzyme esterified yeast transferRNA at about 60% of the rate obtained with E. coli transferRNA.
Zum Vorkommen von Sterinen in Bakterien
Authors: Schubert K. , Rose G. , Wachtel H. , Hörhold C. , Ikekawa N. 
Published: March 2005

Investigations concerning sterols were made in one of strain each of nine species of bacteria and one representative of the basidiomycetes through adsorption chromatography, gas chromatography and mass spectrometry as well as ultraviolet and infrared spectroscopy.Three strains contained sterols in quantities ranging from 0.0004 to 0.01% of the dry weight. In Azotobacter chroococcum six sterols were demonstrated. In six strains sterols were not detectable. The limit of detectability at present is at 0.0001% sterol related to 100 g dry cells.From the extract of Aerobacter cloacae, which contained no sterol, a C16‐hydroxy‐ketone was isolated.
Stereospecific Alkylation with Asymmetric Reagents
Authors: Wallenfels K. , Eisele B. 
Published: March 2005

When undergoing nucleophilic reactions with proteins, α‐iodopropionic acid and its amide show greater specificity for SH groups than to inodoacetic acid and its amide.
The kinetics and sterochemistry of the reactions of the D(+) and L(—) antiopodes of α‐iodopropionic acid and its amide with both eysteine and papain were investigated. The antipodes of the SH reagents reacted with these asymmetric SH compound at different rates. In the reaction with papain, the L(—) antipode of the acid reacted faster than the D(+) antipode; the stereochemical preference was inverted when the amide was used, the D(+)antipode reacting faster than the L(—)antipode.
Arguing from the differing reactivities of the SH reagents and their antipodes and the pH dependence of the reaction rates, it has been suggested, that L(—)α iodopropionic acid is specifically oriented onto the reaction center through the concerted attractive and repulsive actios of a cations and an anionic group in the protein. These have been tentatively identifid as a protonated imidazole residue and a carboxylate group respectively.
Parallels between these stereospecific alkylations and the catalytic action of the enzyme are discussed.
The Cholesterol Side Chain Cleavage Enzymes in Immature Rat Ovary
Authors: Sulimovici S. , Boyd0 G. S. 
Published: March 2005

Cholesterol side chain cleavage reaction has been studied in ovaries of immature female rats pretreated with pregnant mare serum gonadotrophin and human chorionic gonadotrophin. The cleavage enzymes were found to be in the mitochondria and to have the characteristics of a mixed function oxidase requiring NADPH and oxygen. Using [4‐14C]cholesterol as substrate the main product obtained was progesterone while pregnenolone and 20α‐hydroxypregn‐4‐en‐3‐one, were formed in smaller amounts. This shows that ovarian mitochondria contains a Δ5–3β‐hydroxysteroid‐dehydrogenase, a Δ 5–6/4–5 isomerase and a 20α‐hydroxy steroid dehydrogenase. The proposed intermediates in cholesterol side chain cleavage (20α‐hydroxy cholesterol and 20α, 22ɛ‐dihydroxy cholesterol) were not detected.Mitochondrial production of progesterone in the presence of NADPH was further stimulated by succinate while fumarate was without effect. In the presence of NADPH, NADH was found to be inhibitory while NAD+ gave rise to an increase in pregnenolone, the overall reaction being unaffected. Excess of NADPH causes an accumulation of pregnenolone and slightly decreases the overall reaction. The action of reduced glutathione (GSH) and ascorbic acid‐like reducing agents of physiological occurrence has been studied. It was found that GSH in small amounts stimulates and in larger amounts inhibits the side chain cleavage reaction. Ascorbic acid in physiological amounts produced an inhibitory effect.The action of adenosine 3′,5′‐cyclic‐monophosphoric acid (3′5′AMP) and other nucleotides (AMP, ADP, ATP) was tested. 3′5′AMP markedly stimulates the conversion of cholesterol to pregnenolone and decreases the synthesis of progesterone. The action of AMP shows some similarities with that of 3′5′AMP but the action of ADP and ATP was found to be different.