bluuebunny/crossref_metadata_2025_split huggingface dataset:
Propertis of Phosphatidate Phosphohydrolase
Authors: Mitchell Martin P. , Brindley David N. , Hübscher Georg 
Published: March 2005

A study was made of factors affecting the activity of the soluble phosphatidate phosphohydrolase which acts preferentially on membrane‐bound phosphatidate. The requirement for Mg++ was demonstrable only after exhaustive treatment of the membrane‐bound substrate with EDTA and sonication. An analysis of the reaction products indicated that the enzyme did not act on lysophosphtidate.
An indication of the substrate specificity of the soluble phosphatidate phosphohydrolase was obtained with preparations from cat intestinal mucosa by determining its stimulating effect on microsomal glyceride formation from glycerolphosphate and various fatty acids ranging from C6:0 to C18:0 and including C18:1. Maximum stimulation was obtained with oleate incorporation while the stimulation of incorporation of all saturated acid was far lower. Of these, the incorporations of palmitate and myristate were stimulated to the greatest extent.
A more direct assessment of the substrate specificities of soluble and particulate phosphatidate phosphohydrolases was obtained with preparations from rat liver by using membranebound phosphatidates of various fatty acid compositions as substrates. The soluble enzyme had the greatest activity with dimyristoyl and palmitoyl‐oleoyl phosphatidates, whilst dilauroyl and distearoyl phosphatidates were poor substrates. The particulate enzyme had in general much lower activities which were highest with distearoyl and dioleoyl phosphatidates.
Microsomal biosynthesis of phosphatidylcholine as determined by the incorporation of sn‐[1,3‐3H2]glycerol 3‐phosphate was enhanced by the addition o9f particle‐free supernatant indicating that the soluble phosphatidate phosphohydrolase is also important for the conversion of phosphatidate to that diglyceride which is subsquently incorporated into phosphatidylcholine.
Conductimetric Enzyme Assays
Authors: Lawrence Anthony J. 
Published: March 2005

A direct reading, six channel conductivity recording apparatus has been constructed and used to assay enzymes, including some of those found in muscle. This paper gives the essential theory of the method, and indicates that it is a highly versatile assay system. It may be applicable whenever ionic substrates are involved, but this is more easily tested by experiment than by calculation. The manipulation involved in an assay is probably less than in any other method.Conductimetry could be used as a kinetic method for some enzymes (for example amidases), but suffers from restrictions in the amounts of non‐reacting ionic species which can be tolerated.Improvements in the temperature control of the apparatus could allow much higher sensitivity to be used.
Sur la structrue chimique des cires D, peptidoglycolipides macromoléculaires des souches humaines de Mycobacterium tuberculosis
Authors: Markovits Judit , Vilkas Erna , Lederer Edgar 
Published: March 2005

A sample of Wax D, a macromolecular peptidoglycolipid of Mycobacterium tuberculosis, was purified by column chromatography on silicic acid and then analysed. It contains about 90% of a mycolate of arabinogalactan and 8% of a phosphorylated mucopeptide.The structure of the mycolate of arabinogalactan shown in Fig.2 is based on the isolation of the following products of partial hydrolysis: (a) mycolates of arabinofuranose and arabinobiose, in which mycolic acids are esterified to the 5‐OH of arabinofuranose; (b) a 1→4 diagalactopyranoside; (c) a 1→4 arabinogalactoside; (d) an arabinodigalactoside having two 1→4 linkages.The structure of the phosphorylated mucopeptide is shown in Fig. 3 B, as compared to that proposed by Migliore and Jollès [30] (Fig. 3 A). The discrepancy between these two structures might be due to different methods of purification of Wax D and of isolation of the mucopeptide.These results as well as previous work of Azuma et al. [21], Migliore and Jollès [30], Kanetsuna and San Blas [32] lead to a hypothetical structure of Wax D shown in Fig.4.The origin of Wax D is discussed; as already suggested by work of Kanetsuna and San Blas [32] and David et al. [34], Wax D is thought to be the result of partial enzymatic degradation of the cell wall.
Involvement of 1‐Methyladenosine and 7‐Methylguanosine in the Three‐Dimensional Structure of (yeast)tRNAPhe
Authors: Igo‐Kemenes Tibor , Zachau Hans G. 
Published: March 2005

The role 1‐methyladenosine and 7‐methylguanosine in the structure and function of (yeast)tRNAPhe was investigated by studying the NaBH4‐reduction of this RNA, of fragments containing 1‐methyladenosine and 7‐methylguanosine and of the nucleosides themselves.

Treatment of 1‐methyladenosine with NaB3H4 yielded 1‐methyl‐6[3H]hydroadenosine which was fairly stable when kept under a nitrogen atmosphere in a weekly acidic solution. 1‐Methyladenosine was converted to the reduction product when it was part of an octanucleotide or of a fragment comprising the CCA‐half of (yeast)tRNAPhe, but it was not reduced when it was part of intact (yeast)tRNAPhe.
The reduction product of 7‐methylguanosine, 7‐methyl‐8‐hydroguanosine, was too unstable to be isolated under the conditions of oligonucleotide analysis. The reduction of 7‐methyl‐guanosine and the reoxidation could be followed, however, by measuring the absorption of the reduction product at 310 nm. It turned out that also 7‐methylguanosine was reduced when part of an oligonucleotide or a larger fragment of the tRNA while it was protected in the intact (yeast)tRNAPha.
The finding that in intact tRMA 1‐methyladenosine and 7‐methylguanosine are inaccessible to NaBH4 demands a revision of parts of the current three‐dimensionalmodels of tRNA. Our results support the hypothesis that it is the function of the positively charged odd nucleosides, as 1‐methyladenosine and 7‐methylguanosine to stabilize certain regions of the tRNA structure.
The amino acid acceptance of mixtures of CCA‐and pG‐halves of (yeast)tRNAPhe was not altered when 1‐methyladenosine was reduced. 1‐Methyladenosine is therefore probably not an essential part of the synthetase recognition site of this tRNA.
kinetic Studies on the Reaction Mechanism and the Citrate Activation or Liver Acetyl Coenzyme A Carboxylase
Authors: Hashimoto Tkashi , Numa Shosaku 
Published: March 2005

Kinetoc studies were carried out on the reaction mechanism of rat liver acetyl coenzyme A carboxylase. The results of initial velocity and product inhibition studies on the forward and reverse reaction indicate that the carboxylase reaction is most likely to proceed through the “bi bi uni uni ping pong” mechanism. The order of the addition of substrates to the enzyme is as follos: ATP, HCO3‐ and acetyl‐CoA in the forward reaction, and malonyl‐CoA, Pi and ADP in the reverse reaction.Kinetic analysis of the stimulatory effect of citrate on the initial velocities of the forward and reverse reaction indicate that the site of citrate action during catalysis lies predominantly onthe earboxylated enzyme. It is proposed that there exists and equilibrium between active and inactive forms of the carboxybiotinyl enzyme and that this equilibrium is shifted toward the active form in the presence of citrate.
Porcine Luteinizing Hormone and its Subunits
Authors: Hennen Georges , Prusík Zdeněk , Maghuin‐Rogister Guy 
Published: March 2005

A new method is described for the isolation of the subunits of porcine luteinizing hormone which have not been characterized before. By chromatography on SE‐Sephadex C‐25 in 8 M urea, the two subunits LHα and β were obtained in good yield and without apparent cross contamination. The physicochemical and immunological properties of these subunits were studied. Unlike the bovine or ovine LHβ subunits described earlier, porcine LHβ subunit doest not contain lysine.Porcine LHα subunit is electrophoretically heterogeneous and two components represented by two homogeneous electrophoretical zones were isolated and characterized. The amino acid composition of these componetns is very similar; they differ, however, slightly in peptide maps of their tryptic digests.Whole LHα subunit was submitted to specific cleavage at methionine residues by cyanogen bromide and a homogeneous peptide not containing homoserine was isolated. The latter represents most probably the C‐terminal fragment of LHα subunit. Its partial amino‐acid sequence and composition is: Gly‐Asn‐Ala‐Arg‐Val‐Glu‐(His3,Lys,CM‐Cys3‐4,Asp,Thr2,Ser,Glu,Tyr2)‐Ser.The fragment contains 34% of sugar (by weight). In view of the similarity in peptide maps and the unambiguous sequence described above, the primary structure of the different components of LHα subunit must be very similar.
Immunological Studies of Plant Hormones
Authors: Fuchs Sara , Haimovich Joseph , Fuchs Yoram 
Published: March 2005

Specific antibodies to two plant hormones, namely indole‐3‐acetic acid and gibberellic acid, were producd in rabbits which were immunized with conjugates of either hormone to hemolocyanin. The Specific antiboddies obtained were used for assaying the hormones by several immunological assays. The most sensitive assay reported in this paper, for the determination of indole‐3‐acetic acid and gibberellic acid, is the inhibition of inactivation of modifed bacteriphage. For this assay conjugates of either hormone with bacteriophage T4 were prepared and characterized. Such chemically modified bacteriophahges were completely inactivated by the respective specific antiserum and this inactivation was inhibiteid by the free hormone.The specificity of the antibodies produced was tested by a series of cross‐reactions. There was no immunological cross‐reaction between the two hormones which can, therefore, be determined independently. However, antibodies to indole‐3‐acetic acid cross‐reacted with chemically related compounds such as indoelcetyl‐ɛ‐amino carporic acid, tryptamine and truyptophan. The immunological specificity of different gibberellins tested was found to bne in good correlation with the biological specificity.
Mise en évidence dans les mitochondries des cellules de Mammifères de particules ribosomales se différenciant des ribosomes cytoplasmiques par leur taille et leurs acides nucléiques
Authors: Houssais Jean‐François 
Published: March 2005

Evidence showing the presence of 61 S, 46 S and 35 S ribosome‐like particles in mitochondria of mammalian cells (a permanent line of mouse cells (LMTK‐) CI.1d, and mycoplasma‐free HeLa cells, is described.The two known techniques for isolating the mitochondira were used and compared: method I involves the use of EDTA and prevents large contamination by the cytoplasmic ribosomes; method II is based on the use of high concentration of magnesium and NH4Cl, and is thought to give better protection of the mitochondrial ribosomes. Method II applied to mammalian cells gives larege contaimination by cytoplasmic ribosomes, but it is shown that it does not prevent the study of the mitochondiral particles.The 61 S, 46 S and 35 S particle exhibit a ribosomalbehaviour at different magnesium conentrations: the 46 S and 35 S peaks increase at the expense of the 61 S peak at low magnesium concentration. The 80 S peak obtained by method II is shown to contain exclusively cytoplasmic ribosomes as indicated by base composition.RNA was extracted and purified from whole mitochondira isolated by method I and II. The RNA species obtained by method I were the already known 16 S, 12 S, and 4 S mitochondiral RNA species. The RNA species obtaiend by method II were the 28 S cytoplasmic RNA and 18 S RNA. The proporation of the latter was however large than expected. No clear 16 S and 12 S RNA were seen between the large 18 S and the 4–5 S RNA. Base composition of the 18 S RNA proved to be different from that the 18 S cytoplasmic RNA, with a higher content of cytosine and adenine, and lower of guanine. On the other hand, the RNA extracted from the mixture of 61 S and 46 S particles obtained from mitochondria isolated by method I, gave the 16 S, 12 S and 4 S species, the 12 S species predominating. In order to define more precisely the RNA molecules of the 61 S and 46 S particles (obtained from mitochondira isolated by method II) their RNAs were extractd using the RNase inhibitors polyvinylsulfate and diethylpyrocarbonate. The base compositions of these RNAs are very similar. They differ both from the 28 S and 18 S cytoplasmic RNAs and the 16 S and 12 S mitochondrial RNAs by the proportions of cytosine, adenine and guanine. The analysis on surcrose grdient of the RNA of the 61 S particle has shown that it comprises to RNA molecules: an 18.6 S molecule migrating a little farther than the 18 S cytoplasmic RNA, and a 16 S molecule. Essentially a single RNA species was found in the 46 S particle which is 18.6 S.Since a very strong nuclese activity in the mitochondrial lysates in the absence of nuclease inhibitors is observed the possible effect of nucleases on the measured size of ribosome‐like particles, and on the RNA species characterized, are discussed. Our data suggest that the 16 S and 12 S mitochondiral RNAs might be party degraded products of larger molecules.
A Comparison of Five Genetically Distinct Invertases from Saccharomyces
Authors: Ottoleghi Paul 
Published: March 2005

The β‐D‐fructofuranoside fructohydrolases (invertases) of Saccharomyces under the control of the non‐alleic genes SU‐1, SU‐2, SU‐3, SU‐4, and SU‐5 have been examined with respect to the effect of pH on the Michaelis contstants and maximum vlocities of their hydrolysis of sucrose.In every case, the two molecular forms of each invertase (the large extracellular form and the small intracellular form) appeared to be identical as far as the reaction kinetics, but between the different invertases both similarities and differences exist.If quasi‐equilibrium is assumed to be operative, the reaction of all the invrtases fits a model according to which the enzyme‐substrate complexes of all five invertases behave, kinetically, in identical manner. The unsubstrated enzymes, on the other hand, show small but definite differences: SU‐1 and SU‐4 invrtases and SU‐2, SU‐3 and SU‐5 invertases form two groups within which the enzymes respond in essentially identical manner to variations in the environmental pH. SU‐2 invertase can be separated from the second group as it is unique among the five invertases studied in being inhibited by o‐dianisidine.
Isolement et identification de 4 UDP‐trisaccharides dans la glande mammaire et le colostrum de brebis
Authors: Denamur Robert E. , Gaye Pierre J.‐B. 
Published: March 2005

4 UDP‐trisaccharides present in the mammary gland and colostrum of the ewe were isolated and identified. The nucleotides, extracted by means of trichloracetic acid, were purified in the following way : 2 ion‐exchange chromatographies on Dowex 1 (formate), filtration on Sephadex G‐25, paper electrophoresis, pH 5, followed by paper chromatography in 3 different solvents. Using these fractionation techniques, 4 uridine derivatives (X1′, X2′, Y1′, Y2′,) with positive reaction to the Warren neuraminic acid test, were obtained.UDP‐5′, which constitutes the nucleotidic part of the 4 derivatives, was defined more accurately after various acid or enzymatic analyses. The isolation of UDP‐5′ was made by ionexchange or paper chromatography and the total and labile phosphate was estimated. The Warren positive substances released from X1′, X2′, Y1′, Y2′, by neuraminidase or mild acid hydrolysis were identified as N‐glycolyl‐neuraminic acid for the X1′, Y2′ nucleotides, and N‐acetyl‐neuraminic acid for the X2′, Y2′ nucleotides.The behaviour of asialylated nucleotides to ion‐exchange and paper chromatography is described as well as that of asialylated oligosaccharides. The 4 asialylated oligosaccharides contain galactose and an N‐acetyl‐D‐hexosamine, the latter being N‐acetyl‐D‐glucosamine in the case of X1′ and X2′, and N‐acetyl‐D‐galactosamine in the case of Y1′ and Y2′. Total analysis of UDP‐oligosaccharides shows a 1:1:1:1 ratio between uridine, N‐acetyl‐D‐hexosamine, galactose, and neuraminic acid.The 1‐P‐trisaccharides and the trisaccharides were identified after phosphodiesterase hydrolysis followed by phosphatase hydrolysis. The N‐acetyl‐D‐hexosamine carried the reducing group (sodium borohydride). Some structural characteristics of the 4 nucleotides were determined using β‐galactosidase, neuraminidase, periodate, and periodate borohydride. Two of the nucleotides contain N‐acetyl‐glucosamine and are identical to those previously isolated from the goat colostrum. As for the two others, containing N‐acetyl‐galactosamine and appearing as new trisaccharide nucleotides, we may, on the basis of the results obtained, suggest the following sequences:a) UDP‐N‐acetyl‐D‐galactosamine (3←1) D‐galactose (6←2) N‐acetyl‐neuraminic acid;b) UDP‐N‐acetyl‐D‐galactosamine (3←1) D‐galactose (6←2) N‐glycolyl‐neuraminic acid. The possible role of these new nucleotides is discussed.
The Atomic Structure of Erythrocruorin in the Light of the Chemical Sequence and its Comparison with Myoglobin
Authors: Huber Robert , Epp Otto , Steigemann Wolfgang , Formanek Helmut 
Published: March 2005

The atomic structure of the monomeric insect haemoglobin is closely similar to the structure of whale myoglobin, although only about 20% of the amino acids are identical in both protein molecules.A quantitative comparison of both structures, however, showed that in the vicinity of some amino acid substitutions considerable changes occur. The comparison also revealed unexpected long range structural changes induced by amino acid deletions. In particular a deletion of four amino acids in the A B corner shifts the whole helix B considerably.The general distribution of amino acids in erythrocruorin is analogous to that which has been found in other haemoglobin molecules. The large proportion of phenylalanines in the hydrophobic core of the molecule is remarkable. Also the haem pocket is lined with seven phenylalanine side chains. Four of these are unknown in vertebrate haemoglobins.The distal histidine E 7, which is invariant in all known vertebrate haemoglobins, is replaced by a glutamic acid, which has no haem contact, but protrudes into the surrounding solution. This proves that a histidine or another polar residue is not essential for the function of a haemoglobin molecule as a reversible oxygen carrier.
Spécificité de la protéase neutre de Micrococcus caseolyticus
Authors: Desmazeaud Michel J. , Hermier Jean H. 
Published: March 2005

The specificity of an exocellular neutral protease produced by Micrococcus caseolyticus has been investigated with amides, dipeptides mono‐and di‐substituted dipeptides and glucagon. This protease does not exhibit exopeptidase activity: it splits neither amides : Leu(NH2), Phe(NH2), Ala(NH2), Val(NH2), Ileu(NH2), nor Gly‐Leu, Gly‐Phe, Gly‐Ala, nor Z‐Gly‐Leu, Z‐Gly‐Phe, Z‐Gly‐Phe, Z‐Gly‐Ala. There is no free amino acid in glucagon digests. Therefore this protease has to be considered as an endopeptidase. Moreover it splits neither AcTyrOEt or BzTyrOEt (chymotrypsin substrates) nor TosArgOMe or BzArgOEt (trypsin substrates).The results obtained with disubstituted dipeptides Z‐Gly‐X(NH2) indicate that the peptide bonds which are hydrolyzed by the neutral protease were those involving amino groups of hydrophobic amino acids (Phe, Leu, Ala, Val, Ileu but not Trp) or of tyrosine. The highest rate of hydrolysis was obtained with Z‐Gly‐Phe (NH2); it was 1.48 micromoles per minute per mg of protease at 37°C. The second residue (X′) involved in the bond by the carboxyl group in the series Z‐X′‐Phe(NH2) has also an important effect on enzymic activity. So the rates of hydrolysis (in micromoles per min per mg of protease, at 37°), were: 2.01 for Z‐Ala‐Phe(NH2), 1.48 for Z‐Gly‐Phe(NH2) 0.25 for Z‐Leu‐Phe(NH2), 0.146 for Z‐Ser‐Phe(NH2), 0.140 for Bz‐Gly‐Leu(NH2) and 0.122 for Z‐Gly‐Val(NH2).This specificity has been confirmed with glucagon. Peptide bonds in which phenylalanine, leucine or alanine are involved by their amino group are rapidly split.The M. caseolyticus neutral protease displays a substrate specificity which is similar to that found for Pseudomonas aeruginosa or Streptomyces griseus. Thus the hydrophobic nature of the specificity of the protease of M. caseolyticus is not as absolute as that for the megateriopeptidase of Bacillus megaterium.
The Elastase‐Like Enzymes from Streptomyces griseus (Pronase)
Authors: Gertler Arieh , Trop Moshe 
Published: March 2005

Three elastase‐like enzymes, designated Enzyme I, II and III, were purified from a commercial preparation of Streptomyces griseus (pronase) by successive chromatography on DEAE‐cellulose at pH 9.5 and CM‐cellulose at pH 5.5.
Electrophoresis on cellulose acetate at pH 6.9, on polyacrylamide gels at pH 4.5 and 9.5 and exclusion chromatography on Sephadex G‐75 indicated that all three fractions were essentially homogenous.
The amino acid composition of the three enzymes was determined and their molecular weights were estimated by gel‐chromatographic methods.
All three enzymes possess strong esterolytic activity when assayed on a specific elastase substrate N‐acetyl‐L‐alanyl‐L‐alanyl‐L‐alanine methyl ester (AcAla3OMe) and are active, to a smaller extent, on N‐acetyl‐L‐tyrosine ethyl ester. Their activity on α‐N‐benzoyl‐L‐arginine ethyl ester was negligible. All the enzymes have strong proteolytic activity at slight alkaline pH and Enzyme II and III possess also an elastolytic activity on congo red elastin.
All three enzymes are inhibited by diisopropylfluorophosphate. Enzymes II and III were slowly inhibited by N‐tosyl‐L‐phenylalanine chloromethane. Enzyme I was inhibited by the esterolysis products of AcAla3OMe, thus indicating that the same active site controls both esterolytic activities.
A Comparison of Nucleotide Sequences from Mitochondrial and Cytoplasmic Ribosomal RNA of Aspergillus nidulans
Authors: Verma Inder M. , Edelman Marvin , Littauer Uriel Z. 
Published: March 2005

The nucleotide fragments arising from digestion of Aspergillus nidulans mitochondrial and cytoplasmic ribosomal RNAs with T1 ribonuclease have been compared by means of two dimensional ionophoresis. Major qualitative and quantitative differences were found to exist between the two ribosomal RNA species. In addition, distinct differences were observed between the fingerprint patterns of the heavy and light components within each ribosomal RNA sample. The larger component of mitochondrial ribosomal RNA presented a more complex ionophoretic pattern than the smaller one, implying that the former was not a simple dimer of the latter.It is concluded that the nucleotide sequence of the mitochondrial rRNA differs from that of the homologous cytoplasmic rRNA species.