bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis of messenger ribonucleic acid in excised pea-seedling root segments. Separation of the messenger from microsomes by electrophoresis
Authors: Loening UE
Published: August 2015

1. Electrophoresis on cellulose acetate membrane in a tris-pyrophosphate buffer was used to separate microsomal fractions into three components: (1) the lipoprotein; (2) the nucleoprotein (termed the beta-band); (3) traces of free RNA (termed the alpha-band). In tris buffer containing Mg(2+) the alpha-band was not obtained. 2. The incorporation of uridine and phosphate into RNA by excised pea-seedling root segments was studied by using this electrophoretic technique. 3. It was shown that after a short (;pulse') incubation in the radioactive precursor and a longer (;chase') incubation in the non-radioactive precursor most of the incorporation was into the RNA of the alpha-band and little into that of the beta-band. Previous work showed that in roots of whole seedlings the incorporation is mostly into the ribosomal RNA, corresponding to the material in the beta-band. 4. A pulse-labelled RNA has also been found; this seems to be a cell fraction distinct from the microsomes or ribosomes. 5. The apparent base compositions of labelled RNA in the alpha-band and small amounts of labelled RNA in the beta-band and of unfractionated RNA were very different from the composition of ribosomal or transfer RNA, and somewhat like that of DNA. 6. It is suggested that the excised root segment synthesizes a messenger-RNA fraction labelled after a pulse incubation and a distinct messenger RNA labelled after a pulse and chase incubation, but no ribosomal or transfer RNA. The system is thus similar to the; step-down' culture conditions in bacteria.
The assimilation of acetate and propionate by Prototheca zopfi
Authors: Lloyd D , Callely AG
Published: August 2015

1. The tricarboxylic acid and glyoxylate cycles are of major importance in the assimilation of acetate and propionate by Prototheca zopfii. The pattern of assimilation of [2-(14)C]acetate and [2-(14)C]propionate by whole cells growing with their respective substrates is similar except that, with propionate, beta-hydroxypropionate is the first labelled intermediate detected. 2. Carbon dioxide fixation is of little quantitative importance for the growth of this organism with propionate. 3. The yield of cells obtained/mole of acetate is similar to that obtained/mole of propionate and about half that obtained/mole of n-butyrate, these substrates acting as sole sources of carbon and energy.
Effects of vitamins A and D on the biosynthesis of l-ascorbic acid by rat-liver microsomes
Authors: Ghosh NC , Chatterjee I , Chatterjee GC
Published: August 2015

1. The synthesis of l-ascorbic acid from either d-glucuronolactone or l-gulonolactone by liver microsomes of rats is decreased under conditions of hypervitaminosis A; under hypervitaminosis D the synthesis from d-glucuronolactone is increased and that from l-gulonolactone is not affected. 2. The microsomal conversion of l-gulonolactone into l-ascorbic acid is impaired in liver tissues of rats made deficient with respect to either vitamin A or vitamin D when compared with the controls maintained on stock diet.
Pathways of fructose conversion into glucose in foetal rat liver
Authors: Ballard FJ
Published: August 2015

1. Glucose, formed from [1-(14)C]fructose or [6-(14)C]fructose in rat-liver slices, has been isolated as gluconate and degraded to give the radioactivity in C-1, C-2-5 and C-6. 2. By using this method it has been shown that, in liver from foetal rats younger than 20 days, glucose is formed from fructose without splitting of the molecule by the aldolase reaction. The rate of glucose formation from fructose in liver from these foetuses is approximately half of the rate in adult liver. 3. The direct conversion of fructose into glucose in foetal rat liver is not via sorbitol as in seminal vesicles, as this pathway cannot be detected. 4. When liver slices are incubated with [U-(14)C]fructose of high specific activity, the labelled intermediates are similar whether from liver from 18-day foetal, newborn or adult rats. 5. These findings are discussed with reference to the changing pathways of fructose metabolism during perinatal development of the liver in the rat.
Incorporation of sulphate by chick-embryo corium. Nature and products of the process in vitro
Authors: Noble NL , Boucek RJ
Published: August 2015

1. The incorporation of sulphate into the trichloroacetic acid-precipitable fraction of 9-day chick-embryo corium, incubated in Krebs-Ringer phosphate buffer, pH7, is dependent on the sulphate concentration of the medium. Uptake of sulphate is linear with time for 3.5-4hr. and is maximal at 37.5 degrees in the presence of air or oxygen. d-Glucose stimulates the incorporation of sulphate but l-glutamine has no effect. 2. Incorporation of sulphate by the chick corium is enzymic and apparently involves the synthesis of active sulphate (adenosine 3‣-phosphate 5‣-sulphatophosphate) and the transfer of sulphate from adenosine 3‣-phosphate 5‣-sulphatophosphate to acceptor glycosaminoglycuronoglycan. This proposal on the nature of the process is suggested by the similarity between the energy of activation calculated for sulphate-incorporation in the chick-corium preparation and the energy requirement reported for sulphate-activation with purified yeast enzymes. 3. The 9-day chick-embryo corium is composed principally of fibroblasts; there are no histologically demonstrable mast cells. The young fibroblast is apparently responsible for the incorporation of sulphate into glycosaminoglycuronoglycans tentatively identified as chondroitin sulphate(s), heparan sulphate and heparin-like material.
Isolation and identification of a pepsitensin
Authors: De Fernández MT , Paladini AC , Delius AE
Published: August 2015

1. From ox plasma incubated with pepsin a highly purified pepsitensin has been isolated by fractional precipitation, solvent extraction, column chromatography, countercurrent distribution and paper chromatography. 2. Comparison of the properties of this substance with those of synthetic valyl-5 angiotensin I showed: (a) the same specific pressor activity; (b) the same amino acid composition; (c) identical paper-electrophoretic mobilities at various pH values. 3. N- and C-Terminal studies carried out on the intact polypeptide and on the products of chymotrypsin digestion established the following sequence for the amino acids present in the molecule: Asp-Arg-Val-Tyr-Val-His-Pro-Phe-His-Leu. This structure is identical with that of valyl-5 angiotensin I.
Influence of some mononucleotides and their corresponding nucleosides on the metabolism of carbohydrates in the isolated rat diaphragm muscle
Authors: Beloff-Chain A , Betto P , Bleszynski W , Catanzaro R , Chain EB , Dmitrovskii AA , Longinotti L , Pocchiari F
Published: August 2015

1. The influence of ATP on glucose metabolism was studied in the isolated rat diaphragm; it was shown that ATP increases the oxidation of glucose and the aerobic conversion of glucose into lactate, whereas it decreases glycogen synthesis. There was no influence of ATP on the anaerobic formation of lactate from glucose. 2. A maximum effect of ATP on the oxidation of glucose (about 160% increase) was obtained in the presence of 10mm-ATP; in the presence of 2mm-ATP the effect was about 65%, and was approximately constant from 10 to 90min. incubation period. 3. In a phosphate-free tris-buffered medium the oxidation of glucose was considerably decreased, but the percentage stimulation by ATP was about the same as in a phosphate-buffered medium. 4. ATP was shown to increase the oxidation of fructose, glucose 6-phosphate, glucose 1-phosphate, fructose 1,6-diphosphate and, to a much smaller extent, pyruvate. 5. ADP stimulated the oxidation of glucose to the same extent as ATP at a concentration of 2mm and the effect with AMP was only slightly less; IMP and adenosine had only a small stimulatory effect at this concentration, whereas inosine had no effect.
Utilization in vivo of glucose and volatile fatty acids by sheep brain for the synthesis of acidic amino acids
Authors: O'Neal R M , Koeppe R E , Williams E I
Published: August 2015

1. Free glutamic acid, aspartic acid, glutamic acid from glutamine and, in some instances, the glutamic acid from glutathione and the aspartic acid from N-acetyl-aspartic acid were isolated from the brains of sheep and assayed for radioactivity after intravenous injection of [2-(14)C]glucose, [1-(14)C]acetate, [1-(14)C]butyrate or [2-(14)C]propionate. These brain components were also isolated and analysed from rats that had been given [2-(14)C]propionate. The results indicate that, as in rat brain, glucose is by far the best precursor of the free amino acids of sheep brain. 2. Degradation of the glutamate of brain yielded labelling patterns consistent with the proposal that the major route of pyruvate metabolism in brain is via acetyl-CoA, and that the short-chain fatty acids enter the brain without prior metabolism by other tissue and are metabolized in brain via the tricarboxylic acid cycle. 3. When labelled glucose was used as a precursor, glutamate always had a higher specific activity than glutamine; when labelled fatty acids were used, the reverse was true. These findings add support and complexity to the concept of the metabolic; compartmentation' of the free amino acids of brain. 4. The results from experiments with labelled propionate strongly suggest that brain metabolizes propionate via succinate and that this metabolic route may be a limited but important source of dicarboxylic acids in the brain.
Investigation into the distribution and properties of histones and other basic proteins in bacteria
Authors: Leaver JL , Cruft HJ
Published: August 2015

1. Methods have been developed for the extraction and purification of bacterial basic proteins. These proteins were initially examined by a micro-method of starch-gel electrophoresis and were then characterized more fully. 2. Although it was found that most of the DNA in both Bacillus megaterium and Escherichia coli must be free from combination with basic protein, there was some evidence that a small portion might be in the form of a typical nucleohistone complex. 3. The ribosomes of both B. megaterium and E. coli were shown to contain approximately 2% of basic protein. On the basis of ultraviolet-absorption curves, partial amino acid analyses and their behaviour on electrophoresis in polyacrylamide gels, it was concluded that some of these ribosomal basic proteins may be extremely similar to typical histones. 4. These results are discussed in relation to those of other authors, and the possible functions of basic proteins present in micro-organisms are considered with reference to those that have already been proposed for the histones of higher organisms.
The cell wall of Bacillus licheniformis N.C.T.C. 6346. Biosynthesis of the teichuronic acid
Authors: Hughes R.C.
Published: August 2015

1. Particulate fractions prepared from disrupted cells of Bacillus licheniformis N.C.T.C. 6346 catalyse the uptake of radioactivity from UDP-[(14)C]glucuronic acid or UDP-N[(14)C]-acetylglucosamine. Maximal uptake requires the presence of both nucleotides and Mg(2+) ions. The reaction is inhibited markedly by high concentrations of novobiocin and, to a certain extent, by vancomycin and by methicillin. 2. The radioactive product formed is resistant to Pronase and is soluble in 5% (w/v) trichloroacetic acid. It is of high molecular weight, from its behaviour on columns of Sephadex G-50 or G-200, and behaves during paper electrophoresis in n-acetic acid and chromatography on DEAE-cellulose in a manner similar to teichuronic acid. 3. Both teichuronic acid and the synthesized material are resistant to testicular hyaluronidase and to Flavobacterium heparinum heparinase. 4. The specific activity of suspensions of broken cells or of washed particulate fractions is greatest when they are prepared from exponentially growing cells. Fractions obtained from late exponential-phase or stationary-phase cells have very low activity. 5. The galactosamine content of B. licheniformis N.C.T.C. 6346 cell walls increases during the exponential phase and decreases during the stationary phase.
Further studies on the isolation and properties of α-chain sub-units of haemoglobin
Authors: Huehns ER , Shooter EM
Published: August 2015

1. alpha(A)-Chain sub-units have been isolated from neutral haemolysates containing certain unstable beta-chain haemoglobin variants. They are identical, in electrophoretic properties, tryptic peptide analyses and their ability to recombine with Hb-beta(A) (4) at neutral pH, with the alpha(A)-chain sub-units isolated from Hb-A at acid pH. Abnormal alpha(G)-chain sub-units have been prepared from haemolysates containing the alpha-chain variant Hb-G. 2. alpha(A)-Chain sub-units prepared by either method are eluted from Sephadex at low haemoglobin concentration as monomer sub-units. The elution volume, sedimentation coefficient and apparent molecular weight are, however, concentration-dependent, suggesting an equilibrium between monomers and higher polymers with the former as the predominant species. Elevated temperatures cause the alpha(A)-chain sub-unit to aggregate and denature. 3. The product of the reaction between the alpha(A)-chain sub-unit and Hb-beta(A) (4) has been characterized as Hb-A. Only Hb-A and Hb-G can be detected as the products when a mixture of alpha(A)- and alpha(G)-chain sub-units reacts with Hb-beta(A) (4). The absence of the species alpha(A)alpha(G)beta(A) (2) can be explained in terms of the rapid equilibrium between whole and half haemoglobin molecules and the reassortment of alphabeta sub-units during the separation process.
Kinetics of fibrin clot lysis
Authors: Merrills R. J. , Shaw J. T. B.
Published: August 2015

The principles relating the lysis times of fibrin clots to their contents of fibrin, plasminogen and plasminogen-activator were investigated. Mathematical considerations suggested that the square of the lysis time should correlate linearly with the fibrin content, and inversely with the activator and the plasminogen contents of the system. Experimental studies, during which these parameters were independently varied, showed that the predicted relationships were valid for concentrations that gave clot-lysis times in the range normally used for studies of fibrinolysis.
Influence of mitochondrial inhibitors on the respiration and energy-dependent uptake of iodide by thyroid slices
Authors: Tyler D D , Gonze Jeanine , Lamy Françoise , Dumont J. E.
Published: August 2015

The influence of mitochondrial inhibitors, including oligomycin, antimycin and rotenone, on the iodide and oxygen uptake and the nucleotide content of incubated sheep thyroid slices was investigated. Each inhibitor strongly suppressed both iodide and oxygen uptake, and decreased the nucleoside triphosphate content of the slices. In most cases the addition of glucose or mitochondrial substrates restored iodide uptake in inhibitor-treated slices. Inhibitor concentrations sufficient to inhibit iodide uptake strongly had only slight effects on the thyroidal Na++K+-activated adenosine triphosphatase. It is concluded that the inhibitors produce their effects by the inhibition in vivo of mitochondrial oxidative phosphorylation. ATP synthesis appears to be essential for iodide uptake to occur, and the high-energy intermediates (or energized state) of oxidative phosphorylation cannot be used to energize the uptake process. To a limited extent glycolytic ATP synthesis can support iodide uptake, which is therefore not exclusively dependent on aerobic metabolism. The mechanism of energy-linked iodide uptake is discussed.
Factors affecting the glucose 6-phosphate inhibition of hexokinase from cerebral cortex tissue of the guinea pig
Authors: Newsholme E A , Rolleston F. S. , Taylor Kay
Published: August 2015

1. The inhibition of hexokinase by glucose 6-phosphate has been investigated in crude homogenates of guinea-pig cerebral cortex by using a sensitive radio-chemical technique for the assay of hexokinase activity. 2. It was observed that 44% of cerebral-cortex hexokinase activity did not sediment with the microsomal or mitochondrial fractions (particulate fraction), and this is termed soluble hexokinase. The sensitivities of soluble and particulate hexokinase, and hexokinase in crude homogenates, to the inhibitory actions of glucose 6-phosphate were measured; 50% inhibition was produced by 0·023, 0·046 and 0·068mm-glucose 6-phosphate for soluble, particulate and crude homogenates respectively. 3. The optimum Mg2+ concentration for the enzyme was about 10mm, and this appeared to be independent of the ATP concentration. In the presence of added glucose 6-phosphate, raising the Mg2+ concentration to 5mm increased the activity of hexokinase, but above this concentration Mg2+ potentiated the glucose 6-phosphate inhibition. When present at a concentration above 1mm, Ca2+ ions inhibited the enzyme in the presence or absence of glucose 6-phosphate. 4. When the ATP/Mg2+ ratio was 1·0 or below, variations in the ATP concentration had no effect on the glucose 6-phosphate inhibition; above this value ATP inhibited hexokinase in the presence of glucose 6-phosphate. ATP had an inhibitory effect on soluble hexokinase similar to that on a whole-homogenate hexokinase, so that the ATP inhibition could not be explained by a conversion of particulate into soluble hexokinase (which is more sensitive to inhibition by glucose 6-phosphate). It is concluded that ATP potentiates glucose 6-phosphate inhibition of cerebral-cortex hexokinase, whereas the ATP–Mg2+ complex has no effect. Inorganic phosphate and l-α-glycerophosphate relieved glucose 6-phosphate inhibition of hexokinase; these effects could not be explained by changes in the concentration of glucose 6-phosphate during the assay. 5. The inhibition of hexokinase by ADP appeared to be independent of the glucose 6-phosphate effect and was not relieved by inorganic phosphate. 6. The physiological significance of the ATP, inorganic phosphate and α-glycerophosphate effects is discussed in relation to the control of glycolysis in cerebral-cortex tissue.
The purification of luteinizing-hormone-releasing factor with some observations on its properties
Authors: Fawcett C. P. , Reed May , Charlton H. M. , Harris G. W.
Published: August 2015

Bullock median-eminence tissue was used as a source of luteinizing-hormone-releasing factor for small-scale experiments to explore methods for its isolation. The presence of luteinizing-hormone-releasing factor was detected by the ovulation response in rabbits after intrapituitary infusion of the extract. Gel filtration was found to be suitable for the purification of these extracts. The releasing factor appeared to be a basic peptide of molecular weight in the range 1200–2500. On a larger scale, an extract of hypothalamic tissue from sheep was used to establish a multi-stage isolation procedure that resulted in a 200000-fold purification of luteinizing-hormone-releasing factor. After the initial extraction the isolation process consisted of: (1) two cycles of gel filtration; (2) anion-exchange chromatography; (3) gel filtration in a partially organic medium; (4) thin-layer chromatography on cellulose. Stage (3) separated two zones of activity each containing peptides. One of these was purified further by stage (4) to give a preparation that was active at a dose of 6μg. of peptide/animal, although activity diminished seriously during storage. This preparation contained only five or six components, but the small amounts of peptides obtained at this stage of purity were insufficient for full characterization.
Precursors of the pyrimidine moiety of thiamine
Authors: Newell P. C. , Tucker R G
Published: August 2015

1. A method was devised for obtaining the pyrimidine moiety of thiamine in a pure form after its excretion into the medium by de-repressed washed-cell suspensions of mutants of Salmonella typhimurium LT2. 2. By using amino acid-requiring mutants, this excretion of pyrimidine moiety was shown to be dependent on the presence of both methionine and glycine. 3. In the presence of either [Me−14C]methionine or [G−14C]methionine, methionine-requiring mutants did not incorporate radioactivity into the pyrimidine moiety. 4. In contrast, both [1−14C]glycine and [2−14C]glycine were incorporated into the pyrimidine moiety excreted by glycine-requiring mutants, and this occurred with little or no dilution of specific radioactivity. 5. The possible requirement for methionine as a cofactor and the significance of the incorporation of both carbon atoms of glycine are discussed.
The chemical composition of the membranes of protoplasts and L-forms of Staphylococcus
Authors: Ward J. B. , Perkins H R
Published: August 2015

Membrane fractions were prepared from Staphylococcus aureus H and 100 after dissolution of the cell walls by a lytic enzyme from Streptomyces griseus. Membranes were also prepared from the L-forms derived from the same strains. The membranes were analysed for protein, lipid, carbohydrate and RNA contents, and the fatty acid composition of the lipids was determined. A branched-chain saturated C15 acid was the major component in all samples, and the correspondence between L-forms and parent bacteria was fairly close. The lipids were separated into non-polar-lipid, glycolipid and phospholipid fractions; the L-forms contained a little more neutral lipid and much more glycolipid than the parent bacteria. In all membranes the glycolipid, which accounted for all the carbohydrate present, was a diglucosyl diglyceride. The major phospholipids of the protoplast membranes were phosphatidylglycerol and some lipoamino acids (lysine and a little alanine). On the other hand, diphosphatidylglycerol was the chief phospholipid found in L-form membranes.
The distribution of glutamate decarboxylase and aspartate transaminase in subcellular fractions of rat and guinea-pig brain
Authors: Fonnum F.
Published: August 2015

1. The subcellular distributions of glutamate decarboxylase and aspartate transaminase were studied in rat and guinea-pig brain. 2. Glutamate decarboxylase is localized in the synaptosome fraction. The mean density of the particles containing the enzyme is slightly greater than those derived from cholinergic neurones, though overlap is substantial. 3. The enzyme is readily released from synaptosomes by hypo-osmotic treatment, but in the presence of Ca2+, Na+ and K+ it sediments with particulate material. 4. The release and binding of the enzyme to membrane fractions by Ca2+ were investigated. 5. Aspartate transaminase is present in brain as two isoenzymes with different kinetic properties. One isoenzyme is associated with the cytoplasm and the other with mitochondria.
Regulation of choline sulphatase synthesis and activity in Aspergillus nidulans
Authors: Scott J M , Spencer B.
Published: August 2015

1. Choline O-sulphate is taken up from the growth medium to the same extent by sulphur-deficient and sulphur-sufficient mycelia of Aspergillus nidulans, but hydrolysis of the transported sulphate ester in vivo only occurs in the sulphur-deficient mycelia. 2. Choline sulphatase activity could not be detected in vitro in sulphur-sufficient mycelia of wild-type and sulphur mutants of A. nidulans, but after sulphur starvation all strains showed appreciable activity of this enzyme. 3. Optimum activity of choline sulphatase in an ultrasonically treated preparation of sulphur-deficient mycelia was at pH7·5. The optimum substrate concentration was in excess of 25mm and Km was 0·035m. The enzyme was completely inhibited by 10mm-SO32−, PO43−, CN− and cysteine. 4. Growth of sulphur-deficient mycelia on various sulphur sources resulted in a decrease of choline sulphatase activity in vitro. The decrease appeared to be due to a repression of choline sulphatase synthesis rather than to inhibition of activity. De-repression by growth on a sulphur-deficient medium was prevented by cycloheximide. Unlike the choline sulphatase of bacteria the fungal enzyme did not need to be substrate-induced. 5. By using sulphur mutants the identity of the co-repressor was limited to S2O32−, cysteine-S-sulphonate, cysteine or compounds derived directly from them. Circumstantial evidence suggests that the co-repressor is cysteine. 6. Inhibition of choline sulphatase activity in vivo was demonstrated with cysteine as the sulphur source for growth.
Catechol oxygenase induction in Pseudomonas aeruginosa
Authors: Farr D. R. , Cain R B
Published: August 2015

1. The transfer from benzenesulphonate to benzoate as a growth substrate for Pseudomonas aeruginosa strain A resulted in a change in the enzymic route by which catechol was degraded; at intermediate stages it was possible to obtain cells containing the enzymes of both the ‘ortho’ and ‘meta’ metabolic pathways. 2. A similar result was effected by the reverse transfer, benzoate to benzenesulphonate. 3. Catechol itself always elicited a catechol 2,3-oxygenase in uninduced cells, but the product of this reaction, 2-hydroxymuconic semialdehyde, and biochemically related compounds such as 4-hydroxy-2-oxovalerate, unexpectedly induced a catechol 1,2-oxygenase. 4. Both types of catechol oxygenase are strongly repressed by the metabolic end products of both the ‘ortho’ and ‘meta’ pathways, but there was no inhibition of enzymic activity by these end products.
The kinetics of the reduction of isocyanides, acetylenes and the cyanide ion by nitrogenase preparation from Azotobacter chroococcum and the effects of inhibitors
Authors: Kelly M
Published: August 2015

1. Nitrogen-fixing preparations from Azotobacter chroococcum reduced substrates with the following Km values: methyl isocyanide, 1·8×10−4m; ethyl isocyanide, 2·5×10−2m; cyanide ion, 1·4×10−3m; acetylene, 1·2×10−4m. 2. Nitrogen, carbon monoxide or hydrogen competitively inhibited isocyanide reduction with the following Ki values: hydrogen, 1·3×10−3m; carbon monoxide, 6·8×10−6m; nitrogen, 4·3×10−4m. 3. Living nitrogen-fixing bacteria, and isolated clover nodules, formed methane from methyl isocyanide. 4. These results are discussed in relation to other work and possible mechanisms of nitrogen fixation.
Metabolism of pyrithiamine by the pyrithiamine-requiring mutant of Staphylococcus aureus
Authors: Sinha Asru K. , Chatterjee G. C.
Published: August 2015

1. A mutant strain of Staphylococcus aureus that requires pyrithiamine for its optimum growth was found to utilize pyrithiamine during the exponential phase of growth. 2. Pyrithiamine was deaminated by the organism to form oxypyrithiamine, the reaction being enzymic with no cofactor requirement. 3. On prolonged incubation of S. aureus A cultures, the concentration of deaminating enzyme increased in the culture broth, from which pyrithiamine-deaminating enzyme could be isolated by solvent fractionation. 4. Oxypyrithiamine is not a competitive analogue of thiamine although it inhibited the growth of the parent strain of S. aureus; the inhibition index of this compound, however, was lower than that of pyrithiamine.
Subfragments from the Fc fragment of human immunoglobulin G. Isolation and physicochemical characterization
Authors: Turner M. W. , Bennich H.
Published: August 2015

A fragment termed fragment Fc′ and a related fragment termed fragment pFc′ produced by the actions of papain and pepsin respectively on human immunoglobulin G have been isolated and characterized. Amino acid analyses and experiments utilizing cyanogen bromide to cleave the methionyl bonds of the Fc′ and pFc′ fragments make it possible to locate both fragments within the known chain structure of the immunoglobulin G molecule. The pFc′ fragment is probably a non-covalently linked dimer situated at the C-terminal end of the molecule, containing about 232 amino acid residues and having a molecular weight of 26000. The Fc′ fragment is a similar dimer of about 182 residues extending from near residue 14 to near residue 105 (numbered from the C-terminal end) of the γ-chain and has a molecular weight of 21000.
Metabolism of 11-oxygenated steroids. Metabolism in vitro by preparations of liver
Authors: Bush I. E. , Hunter Sheila A. , Meigs R. A.
Published: August 2015

1. The isolation and partial purification of 11β-hydroxy steroid dehydrogenase from rat and guinea-pig liver microsomes has been achieved by conventional methods. 2. The efficiency of different 11-oxygenated steroids as substrates has been examined. The relative efficiencies confirm in the main the stereochemical theory of the enzyme–coenzyme–substrate complex that was proposed earlier on the basis of studies in vivo. Δ4-3-Ketones and 5α-hydrogen steroids are readily metabolized by the enzyme. 5β-Hydrogen steroids and Δ4-3-ketones with certain large α-substituents are metabolized to a limited extent or not at all. Halogen substitution in the 9α-position enhances the rate of reduction of 11-ketones but blocks the oxidation of the related 11β-ols. 3. 9α-Fluorocortisol is a competitive inhibitor of the oxidation of cortisol, but 9α-fluorocortisone is reduced at five to ten times the initial velocity of cortisone. 4. 11β-Hydroxy steroid dehydrogenase activity has been found in liver microsomes of rat, guinea pig, rabbit and calf. 5. Relative substrate efficiencies and Km values are similar in whole (debris-free) homogenates, washed microsomes and acetone-dried powders of washed microsomes. 6. A variety of conditions have been examined for the observation of 11β-hydroxy steroid dehydrogenase activity. NADP(H) is an efficient and NAD(H) a very poor coenzyme for the reaction.
Effect of second-leaf removal or kinetin treatment on the nucleic acid metabolism of senescing first seedling leaf of barley
Authors: Srivastava B. I. Sahai , Atkin Roger K.
Published: August 2015

1. Changes in nucleic acid metabolism in first seedling leaves of barley plants during aging (from 7 to 27 days) were followed, and the effect of continual removal of the second leaf and basal meristem or of treating the first leaf with 20p.p.m. kinetin on these changes was examined. During aging of the first seedling leaves the ribosomal RNA, DNA and soluble RNA declined, with ribosomal RNA showing the most rapid fall. This was, however, accompanied by increased incorporation of 32P into RNA, which reached its peak on the fifteenth day. 2. Second-leaf removal partially suppressed first-leaf senescence as judged by retarded chlorophyll and nucleic acid decline and by a decreased extent of RNA labelling. Treatment with kinetin, however, did not prove effective. 3. No significant differences in the sucrose-gradient pattern of 32P-labelled nucleic acids or in the 32P-labelled nucleotide composition of RNA fractions during aging or during the two treatments were noted, except for a decrease in CMP content of soluble RNA during aging. 4. The results demonstrate that important changes in RNA metabolism are associated with leaf senescence.
The action of digitonin on rat liver mitochondria. Phospholipid content
Authors: Newman H. A. I. , Gordesky Stanley E. , Hoppel Charles , Cooper Cecil
Published: August 2015

1. The amount and types of phospholipid and the fatty acid composition of the various phospholipids were examined in intact rat liver mitochondria, in mitochondria devoid of their outer membrane (preparation A) and in very small pieces derived from the disruption of the inner-membrane complexes (preparation B). The latter two preparations were obtained by digitonin treatment and carry out oxidative phosphorylation. 2. The ratio μg.atoms of phospholipid P/mg. of protein was 0·163 for intact mitochondria, decreased to 0·118 on removal of the outer membrane and increased markedly to 0·292 on disruption of the inner-membrane complex. 3. Examination of the various types of phospholipid present showed that the molar proportions cardiolipin:phosphatidylcholine:phosphatidylethanolamine were approx. 1:6:6 for intact mitochondria and 1:3:3 for preparations A and B. 4. There was a correlation between the recovery of cardiolipin and adenosine triphosphatase activity in the conversion of intact mitochondria into preparations A and B. 5. The fatty acid contents of the various types of phospholipid purified by thin-layer chromatography were identical in all three preparations. Our results show a considerably higher content of arachidonic acid and lower content of oleic acid for phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol than have previously been reported for mitochondrial phospholipids.
Biochemical studies of toxic agents. The metabolic formation of 1- and 2-menaphthylmercapturic acid
Authors: Hyde C. W. , Young L.
Published: August 2015

1. Various derivatives of 1- and 2-methylnaphthalene, of the type C10H7·CH2X, were administered to rats and the urines of the dosed animals were examined for the presence of 1- and 2-menaphthylmercapturic acid by chromatographic and isolation procedures. A similar, but more limited, series of experiments was carried out with rabbits. 2. All the compounds were administered by subcutaneous injection with the exception of S-(1- and 2-menaphthyl)-l-cysteine, which were added to the food. 3. 1-Menaphthylmercapturic acid was isolated from the urine of rats after the administration of 1-menaphthyl chloride, bromide, alcohol, acetate and benzoate, S-(1-menaphthyl)-l-cysteine and S-(1-menaphthyl)glutathione. 4. 2-Menaphthylmercapturic acid was isolated from rat urine after administration of 2-menaphthyl chloride, S-(2-menaphthyl)-l-cysteine and S-(2-menaphthyl)-glutathione, and was detected chromatographically after injecting 2-menaphthyl bromide. 5. The corresponding mercapturic acids were isolated after administering 1- and 2-menaphthyl chloride and 1-menaphthyl acetate to rabbits, but not after giving 1- and 2-menaphthyl bromide and 1-menaphthyl alcohol, although chromatographic evidence of mercapturic acid excretion was obtained after injecting these compounds.
Comparative studies of two types of bovine immunoglobulin G heavy chains
Authors: Milstein C. P. , Feinstein A.
Published: August 2015

‘Fingerprints’ of bovine colostrum and serum immunoglobulin G1 heavy chains were extremely similar, but different from serum immunoglobin G2 heavy chains. Serum immunoglobulin G1 and immunoglobulin G2 heavy chains were treated with cyanogen bromide. The fractions from the C-terminal end of the heavy chains were isolated and the amino acid sequence of this fraction from immunoglobulin G2 was:His-Glx-Ala-Leu-His-Asx-His-Tyr-Met-Gln-Lys-Ser-Thr-Ser-Lys-Ser-Ala-GlyThe amino acid composition of this fraction from immunoglobulin G1 was the same except for the methionine, which in immunoglobulin G1 was replaced by threonine.
Purification, properties and mechanism of action of a staphylolytic enzyme produced by Aeromonas hydrophila
Authors: Coles N. W. , Gilbo C. M. , Broad A. J.
Published: August 2015

1. An enzyme produced by Aeromonas hydrophila and capable of lysing Staphylococcus aureus cells was purified 180-fold by gel filtration and chromatography on columns of AG-50 W resin. 2. Physical measurements on the purified enzyme suggest that it is a small basic protein with an isoelectric point between pH9·0 and pH9·5. 3. Maximum lytic activity was obtained in 20mm-tris–glycine buffer, pH8·5, at 45°, with no detectable activity in the absence of a nitrogenous base. 4. The enzyme is active in the above buffer containing 1·5m-sucrose, and is useful for the preparation of protoplasts of Staphylococcus aureus. 5. Purified cell wall peptidoglycans of two strains of Staphylococcus aureus, differing in amino acid composition, were hydrolysed by the enzyme with the liberation of glycine oligopeptides, principally diglycine and triglycine. 6. Synthetic glycine oligopeptides larger than triglycine, but not polyglycine, were hydrolysed, as were a number of leucine-containing dipeptides and tripeptides, but no proteolytic activity could be demonstrated. 7. It is concluded that the enzyme is lytic towards Staphylococcus aureus because it splits the pentaglycine cross-links of the cell-wall peptidoglycan.
Column chromatography of human small-intestinal maltase, isomaltase and invertase activities
Authors: Dahlqvist A. , Telenius U.
Published: August 2015

1. The maltase, isomaltase and invertase (sucrase) activities of solubilized mucosal preparations from human jejunum and ileum were studied with column chromatography on anion-exchange (diethylaminoethyl- and triethylaminoethyl-)cellulose and Sephadex G-200 gel. 2. On ion-exchange cellulose columns both kinds of enzyme preparations yielded two major disaccharidase peaks. The first peak contained maltase Ia (=isomaltase) and maltase Ib (=invertase). The second peak contained maltase II and maltase III. 3. On Sephadex G-200 gel columns jejunal preparations yielded the corresponding peaks as on ion-exchange columns, but the peaks appeared in the reverse order in the effluent. The ileal preparation studied yielded a single peak on gel columns, containing all the activities studied and eluted with the ‘void volume’. 4. Precipitation with ethanol did not affect the behaviour of the enzymes during ion-exchange chromatography. When gel filtration was performed after ethanol precipitation of the enzymes, however, two peaks were obtained also with the ileal preparation, and subfractionation of the invertase was obtained with both kinds of preparations. 5. The second peak from ion-exchange chromatograms, containing maltase II and maltase III, on concentration was found to have very weak isomaltase activity, probably exerted by these enzymes as such. This activity accounts for only about 1% of the total isomaltase activity of the mucosa. 6. The results support the concept of the specificity of the human small-intestinal disaccharidases previously described after heat-inactivation experiments. The subfractionation of the invertase that under certain conditions is seen on Sephadex G-200 columns appears most likely to be an artifact. Consequently the nomenclature for the human maltose-, isomaltose- and sucrose-splitting enzymes proposed by another research group after gel-filtration chromatography studies should be abandoned. It seems more logical to keep the nomenclature based on heat inactivation [maltase Ia (=isomaltase), maltase Ib (=invertase or sucrase), maltase II and maltase III] until increased knowledge about the specificity and structure of these enzymes makes possible a more rational nomenclature.
The metabolism of polyphosphoinositides in hen brain and sciatic nerve
Authors: Sheltawy A. , Dawson R. M. C.
Published: August 2015

1. The distribution of individual phospholipids was determined in hen brain and compared with that in sciatic nerve obtained in a previous investigation. Sciatic nerve is more enriched in the myelinic phospholipids ethanolamine plasmalogen, phosphatidylserine and sphingomyelin, but it contains relatively less triphosphoinositide, and much less diphosphoinositide, than the brain. 2. The course of incorporation of intraperitoneally injected 32P into the acid-soluble phosphorus, phosphoinositides and total phospholipids of hen brain and sciatic nerve was followed. Although the maximum specific radioactivity in sciatic nerve of acid-soluble phosphorus is 4·5 times, and that of triphosphoinositide six times, that in the brain, the relative rate of triphosphoinositide phosphorus synthesis per gram of brain is three times that in sciatic nerve. 3. Administration of the demyelinating agent tri-o-cresyl phosphate to hens has no significant effect on the amounts or the rate of 32P incorporation into the total phospholipids of the sciatic nerve. However, the rate of incorporation of 32P into triphosphoinositide, although not its concentration, is raised from the first day after administration of the drug and remains thus 13 and 23 days later. 4. The incorporation of 32P into polyphosphoinositides of hen brain slices in vitro was studied. The recovery of triphosphoinositide from the slices is markedly increased in the presence of EDTA, although the rate of incorporation of 32P is unaffected. The incorporation of 32P is dependent on the presence of Mg2+ and Ca2+ in the medium, and is decreased when Na+ is replaced with K+ or cholinium ions.
Studies on alkaline phosphatase. Transientstate and steady-state kinetics of Escherichia coli alkaline phosphatase
Authors: Fernley H N , Walker P. G.
Published: August 2015

1. The transient-state and steady-state phases of the reaction between Escherichia coli alkaline phosphatase and 4-methylumbelliferyl phosphate were investigated by using a fluorimetric stopped-flow technique. 2. At low substrate concentration (5μm) in the pH range 3·8–6·3 there was an initial rapid liberation of up to 1mole of 4-methylumbelliferone/mole of enzyme. 3. At very low substrate concentration (0·1μm) in the pH range 4·9–5·9 an initial lag in 4-methylumbelliferone production was observed, from which values for k+1 and k−1 could be obtained. 4. The pH profiles for the rates of phosphorylation and dephosphorylation are quite different, and it is postulated that an ionizing group which determines the conformation during the phosphorylation step is not involved in the dephosphorylation step. 5. The binding constants for substrate and Pi are similar throughout the pH range 4–8. The ionization of substrate or Pi appeared to have no marked effect on the binding.
Specificity of combination between mucopeptide precursors and vancomycin or ristocetin
Authors: Perkins H R
Published: August 2015

Vancomycin and ristocetin formed complexes on being mixed with mucopeptide precursors from various bacteria, as shown by chromatography, electrophoresis and differential ultraviolet spectra. Equimolar proportions of antibiotic and peptide were present. The specificity of the reaction was studied and the smallest molecule found to react was acetyl-d-alanyl-d-alanine. This C-terminal dipeptide sequence must be present for complex-formation; change of configuration or esterification prevented it. Modified vancomycins that retained antibiotic activity also combined with appropriate peptides. The dissociation constants of the more stable complexes were estimated from the differential-absorption results. The relationship of complex-formation to antibiotic action is discussed. Penicillin, supposed to be an analogue of acyl-d-alanyl-d-alanine, also modified the spectrum of vancomycin; so, too, did sodium benzylpenicilloate.
Conditions for the self-catalysed inactivation of carnitine acetyltransferase. A novel form of enzyme inhibition
Authors: Chase J. F. A. , Tubbs P. K.
Published: August 2015

1. Carnitine acetyltransferase is very rapidly inhibited in the presence of bromoacetyl-(−)-carnitine plus CoA or of bromoacetyl-CoA plus (−)-carnitine. 2. Under appropriate conditions, the enzyme may be titrated with either bromoacetyl substrate analogue; in each case about 1mole of inhibitor is required to inactivate completely 1mole of enzyme of molecular weight 58000±3000. 3. Inhibition by bromoacetyl-CoA plus (−)-carnitine results in the formation of an inactive enzyme species, containing stoicheiometric amounts of bound adenine nucleotide and (−)-carnitine in a form that is not removed by gel filtration. This is shown to be S-carboxymethyl-CoA (−)-carnitine ester. 4. The inhibited enzyme recovers activity slowly on prolonged standing at 4°. 5. Incubation with S-carboxymethyl-CoA (−)-carnitine ester causes a slow inhibition of carnitine acetyltransferase. 6. The formation of bound S-carboxymethyl-CoA (−)-carnitine ester by the enzyme is discussed. Presumably the resulting inhibition reflects binding of the ester to both the CoA- and carnitine-binding sites on the enzyme and its consequent very slow dissociation. These observations confirm that carnitine acetyltransferase can form ternary enzyme–substrate complexes; this also appears to be the case with carnitine palmitoyltransferase and choline acetyltransferase.
Repression by glucose of acetohydroxy acid synthetase in Escherichia coli B
Authors: Coukell M. B. , Polglase W. J.
Published: August 2015

Acetolactate formation in Escherichia coli B results from the activity of a single system, acetohydroxy acid synthetase, which has a pH optimum of 8·0 and is sensitive to end-product inhibition by l-valine. Acetohydroxy acid synthetase was found to be subject to catabolite repression, and the nature and concentration of the carbon source had a greater effect on the formation of the enzyme than had the known end products (valine, isoleucine, leucine and pantothenate) of the biosynthetic pathways of which this enzyme is a member. The results suggest that acetohydroxy acid synthetase may play an amphibolic role in E. coli B.
The cryptic nature of hepatic microsomal sulphite oxidase
Authors: Joshi V. C. , Kurup C. K. Ramakrishna , Ramasarma T.
Published: August 2015

1. The activity of rat liver microsomal sulphite oxidase (EC 1.8.3.1) was increased several-fold on aging of microsomes, on delipidation by extraction with acetone or on solubilization with deoxycholate, suggesting its existence in a cryptic state. 2. In rat liver most of the sulphite oxidase was present in the nuclear fraction and only a small portion in the microsomes. 3. Microsomal sulphite oxidase activity was low in the developing embryo and increased rapidly after birth.
Control of δ-aminolaevulate synthetase activity in Rhodopseudomonas spheroides
Authors: Marriott J. , Neuberger A. , Tait G. H.
Published: August 2015

1. δ-Aminolaevulate synthetase from Rhodopseudomonas spheroides grown semi-anaerobically undergoes a spontaneous activation during the first hour after the disruption of cells when homogenates are stored at 4°. 2. After cultures of R. spheroides growing semi-anaerobically are oxygenated no activation of δ-aminolaevulate synthetase occurs in cell extracts. Cessation of activation in extracts is almost complete 10min. after oxygenation of cells has begun. 3. A heat-stable fraction of low molecular weight from semi-anaerobic cells reactivates δ-aminolaevulate synthetase in extracts of oxygenated cells and appears to contain a compound responsible for the spontaneous activation. 4. A heat-stable fraction of low molecular weight from oxygenated cells inhibits the spontaneous activation in extracts of semi-anaerobic cells. 5. The effect of oxygen on the rate of bacteriochlorophyll synthesis in R. spheroides may be mediated through alterations in the concentrations of a low-molecular-weight activator and inhibitor of δ-aminolaevulate synthetase.
Assay of the possible organization of particle-bound enzymes with squalene synthetase and squalene oxidocyclase systems
Authors: Etemadi A. H. , Popják G. , Cornforth J W
Published: August 2015

Lanosterol was biosynthesized in pig liver homogenate from [4,8,12−14C3]farnesyl pyrophosphate and [4S-4−3H]NADPH through the intermediary formation of squalene labelled asymmetrically with 3H. The biosynthetic lanosterol, freed from labelled 24,25-dihydrolanosterol, which was also synthesized, was converted into 24,25-dihydrolanosteryl acetate and subjected to chemical degradations to locate the position(s) of the 3H label in the molecule. The ratio of 3H at C-11 to that at C-12 was found to be 1·28. Although a certain inequality of labelling was thus indicated, experimental uncertainties did not permit the conclusion that the asymmetrically labelled squalene might have been cyclized preferentially from one end.