共查询到20条相似文献,搜索用时 31 毫秒
1.
Satoshi Ōmura Haruo Tanaka Masaru Tsukui 《Biochemical and biophysical research communications》1982,107(2):554-560
The enzymatic conversion of various tylosin precursors was carried out using a cell-free system of the tylosin producer to determine the order and intermediates of oxidations of the 16-membered branched lactone ring at C-20 and C-23 in the biosynthesis of tylosin. It was found that the order of the oxidation of the lactone is: (1) hydroxylation of 5--mycaminosylprotylonolide at C-20, (2) oxidation of C-20 hydroxymethyl to formyl, (3) hydroxylation at C-23 to give 5--mycaminosyltylonolide. The formation of 23-hydroxy-5--mycaminosylprotylonolide from 5--mycaminosylprotylonolide was not observed. 相似文献
2.
《Insect Biochemistry》1991,21(7):795-801
The egt gene of the baculovirus Autographa californica nuclear polyhedrosis virus encodes an ecdysteroid UDP-glucosyltransferase. The glucoside formed by this enzyme using ecdysone and UDP-glucose as substrates has been purified and structurally characterized by nuclear magnetic resonance spectroscopy and by fast atom bombardment mass spectrometry. These studies have identified the conjugate as ecdysone . Substrate specificity studies have confirmed that ecdysteroids lacking a hydroxyl moiety at C-22 are not substrates for the enzyme. 相似文献
3.
Wilfredo Mellado Neal F. Magri David G.I. Kingston Renee Garcia-Arenas George A. Orr Susan Band Horwitz 《Biochemical and biophysical research communications》1984,124(2):329-336
Synthesis and biological activity of 2′-acetyltaxol and 7-acetyltaxol are reported. Activity is measured by cytotoxicity toward the macrophage-like cell line J774.2, and by promotion of microtubule assembly in the absence of exogenous GTP. Addition of an acetyl moiety at C-2′ results in loss of activity but not cytotoxicity. The properties of 7-acetyltaxol are similar to those of taxol in its effects on cell replication and on microtubule polymerization. Therefore a free hydroxyl group at C-7 is not required for activity and this position is available for structural modifications. 相似文献
4.
J.A. Pérez-González A. Jiménez 《Biochemical and biophysical research communications》1984,125(3):895-901
The paromomycin producing organism is resistant to this antibiotic and contains a phosphotransferase which inactivates paromomycin. The gene encoding this enzyme has been inserted in the vector pIJ702 and then cloned in , selecting for paromomycin-resistance. Three plasmids have been isolated and one of them, pMJ1, contains a 2.2 kb insert with a single HindIII restriction site. Insertion of foreign DNA in this site blocks the expression of the phosphotransferase enzyme indicating that it is within the cloned gene. These findings provide a new dominant selective marker for cloning vectors with the versatility of insertional inactivation. 相似文献
5.
The equilibrium affinity constant for rat prostate androgen receptor and epididymal androgen binding protein (ABP) has been determined for thirty-four potential progestogens. Three A-nor-, four A,19-dinor-, and one A-homo-5α-androstane derivative bind to the androgen receptor (KD<0.5 μM). Five of these compounds also bind to ABP with an affinity of the same order of magnitude. “Anordrin” (compound ) and “Dinordrins” (compounds ), which are potential female contraceptives, do not bind with high affinity to the androgen receptor or to ABP. The following modifications in A-nor derivatives favour binding to the receptor as compared to ABP: 19-nor substitution (compound ), C-18 methyl homologation (compound ), 2α-ethinylation (compound ). One 2α-allenyl A-nor derivative (compound ) and one A-homo derivative (compound ) bind almost exclusively to ABP. The interaction with either binding protein is decreased by oxidation or esterification of the hydroxyl group at C-17, and by addition of a 17 α-ethinyl group. The latter modifications are likely to increase the specificity of androstane derivatives for receptors other than androgen binding proteins, such as the progesterone receptor. 相似文献
6.
M Kahn M Concino R Gromkova S Goodgal 《Biochemical and biophysical research communications》1979,87(3):764-772
Membrane vesicles 40–70NM in diameter have been observed in the supernatant of cultures of a mutant strain of (C-10) defective in transformation. Electron microscopy of thin sections of (C-10) demonstrate that the vesicles are produced by budding off the outer membrane. Vesicles purified by differential centrifugation possess a DNase resistant DNA binding activity, and the membrane-DNA complex has been analyzed on CsCl gradients and shown to band at a density of 1.35g/cc. Mutants of having similiar properties have also been isolated. We report the method of isolation and some of the biochemical properties of vesicles from and . 相似文献
7.
F. Malpartida M. Zalacaín A. Jiménez J. Davies 《Biochemical and biophysical research communications》1983,117(1):6-12
The gene encoding the phosphotransferase enzyme that modifies hygromycin B in its producing organism , has been cloned in the vector pIJ41. Two plasmids, pFM4 and pFM6, containing 2.1 and 19.6 kb inserts of DNA, respectively, which express the modifying enzyme, have been isolated. A 3.1 kb PstI restriction fragment from pFM4 was inserted in the vector pIJ350 and the resulting plasmids, pMZ11.1 and pMZ11.2, express the hygromycin B-resistance phenotype. The utility of this dominant marker for cloning experiments is discussed in the text. 相似文献
8.
The biosynthesis of blood group B determinants by the blood group A gene-specified alpha-3-N-acetyl-D-galactosaminyltransferase 总被引:1,自引:0,他引:1
The blood group gene-specified α-3-N-acetyl-D-galactosaminyl-transferase in human plasma, when concentrated by adsorption onto group O red cell ghosts or Sepharose 4B, catalyses the transfer of D-galactose in α-linkage to low-molecular-weight H-active acceptors. The product synthesised with 2′-fucosyllactose is chromatographically indistinguishable from the blood group B-active tetrasaccharide, Galα1→3[Fucα1→2]Galβ1→4Glc. The optimum pH for the transfer of D-galactose by the -transferase is 7. At this pH the Vmax for the transfer of N-acetyl-D-galactosamine is about 300 times higher than that for the transfer of D-galactose. These results indicate that an -transferase can, under centain conditions, synthesise B determinant structures. 相似文献
9.
[4-14C]Cholesterol was incubated with an adrenocortical preparation in the presence of 16O2 and 18O2 devoid of significant 16O18O. Isolated (20R,22R)-20,22-dihydroxycholesterol was converted to a trimethylsilyl derivative and analyzed by gas chromatography - mass spectrometry to determine the isotope distribution of the oxygen atoms at C-20 and C-22. The ions of 289, 291, and 293 (comprising the C8 C-20 to C-27 side-chain and containing, respectively, 16O2, 16O18O, and 18O2) exhibited a binomial distribution indicating that the oxygen atoms of the vicinal glycol were drawn at random from the atomic pool of the oxygen molecules. If both side-chain hydroxyl groups had originated from the atoms of the same oxygen molecule, the ion of 291 would have been absent. 相似文献
10.
(1) The for 1.3 mM D-allose uptake and efflux in insulin-stimulated adipocytes is 1.7 ± 0.1 min. In the absence of insulin mediated uptake of D-allose is virtually eliminated and the uptake rate () is near that calculated for nonmediated transport. The kinetic parameters for D-allose zero-trans uptake in insulin-treated cells are Kztoi = 271.3 ± 34.2 mM, Vztoi = 1.15 ± 0.12 mM · s?1. (2) A kinetic analysis of the single-gate transporter (carrier) model interacting with two substrates (or substrate plus inhibitor) is presented. The analysis shows that the heteroexchange rates for two substrates interacting with the transporter are not unique and can be calculated from the kinetic parameters for each sugar acting alone with the transporter. This means that the equations for substrate analogue inhibition of the transport of a low affinity substrate such as D-allose can be simplified. It is shown that for the single gate transporter the Ki for a substrate analogue inhibitor should equal the equilibrium exchange Km for this analogue. (3) Analogues substituted at C-1 show a fused pyranose ring is accepted by the transporter. 1-Deoxy-D-glucose is transported but has low affinity for the transporter. High affinity can be restored by replacing a fluorine in the β-position at C-1. The Ki for ; the Ki for . Replacing the ring oxygen also results in a marked reduction in affinity. The Ki for . (4) A hydroxyl in the gluco configuration at C-2 is not required as 2-deoxy-d-galactose (Ki = 20.75 mM) has a slightly higher affinity than d-galactose (Ki = 24.49 mM). A hydroxyl in the manno configuration at C-2 interferes with transport as d-talose (Ki = 35.4 mM) has a lower affinity than d-galactose. (5) d-Allose (Km = 271.3 mM) and 3-deoxy-d-glucose (Ki = 40.31 mM) have low affinity but high affinity is restored by substituting a fluorine in the gluco configuration at C-3. The Ki for . (6) Analogues modified at C-4 and C-6 do not show large losses in affinity. However, 6-deoxy-d-glucose (Ki = 11.08 mM) has lower affinity than d-glucose and 6-deoxy-d-galactose Ki = 33.97 mM) has lower affinity than d-galactose. Fluorine substitution at C-6 of d-galactose restores high affinity. The Ki for . Removal of the C-5 hydroxymethyl group results in a large affinity loss. The Ki. The Ki for . (7) These results indicate that the important hydrogen bonding positions involved in sugar interaction with the insulin-stimulated adipocytes transporter are the ring oxygen, C-1 and C-3. There may be a weaker hydrogen bond to C-6. Sugar hydroxyls in non-gluco configurations may sterically hinder transport. 相似文献
11.
J.P. Van Wauwe F.G. Loontiens C.K. De Bruyne 《Biochimica et Biophysica Acta (BBA)/General Subjects》1973,313(1):99-105
The hemagglutinin from the castor bean (Ricinus communis) shows a precipitin-like like reaction with a series of branched galactomannas, dependent on their galactose: mannose ratio. Charged and neutral linear galactants fail to co-precipitate with the protein. Hapten inhibition of the turbidimetrically assayed hemagglutinin-Lucerne seed galactomannan system incidates that simple sugars such as D-galactose, D-fucose and L-arabinose bind to the protein. Of the glycosides tested, methyl β-D-galactopyranoside is a better inhibitor than the corresponding α-another. is about 10 tiems less effective than , the best inhibitor tested. Equilibrium dialysis data obatined with the latter ligand are consistent with a protein containing two identical and independent binding sites with an intrinsic association constant equal to 1.65 ? 104 l/mole at 25 °C. 相似文献
12.
George N. Phillips Florante A. Quiocho Ronald L. Sass Peter Werness Herschell Emery Furn F. Knapp G.J. Schroepfer 《Bioorganic chemistry》1976,5(1):1-10
Previous studies have established that hydride reduction of 3β-benzoyloxy-5α-cholest-8(14)-en-15-one yields two epimers (at C-15) of 5α-cholest-8(14)-en-3β,15-diol which were designated as diol A and B. Efficient enzymatic conversion of both compounds to cholesterol was observed. To determine the absolute configuration of the 15-OH function in the two compounds, the 3β-p-bromobenzoyl ester of diol B was prepared from 3β-p-bromobenzoyloxy-5α-cholest-8(14)-en-15-one by reduction with sodium borohydride. Crystals of the derivative were found to belong to the space group P1, with unit cell parameters; , , , α = 93.05°, β = 100.27°, γ = 90.82°, and one molecule per unit cell. Least-squares refinement of the structure was carried out to final R value of 0.14. The configuration of the hydroxyl group at the 15 position of diol B has been determined to be β. 相似文献
13.
Rolf Andersson Olle Larm Elisabeth Scholander Olof Theander 《Carbohydrate research》1980,78(2):257-265
Sucrose and (1) were oxidised with bromine in aqueous solution at pH 7 and room temperature. The resulting keto derivatives were converted into their more-stable O-methyloximes, which were characterised by spectroscopic and chromatographic methods. Oxidation of 1 occurred at C-3 and C-5, with a preference for C-5. In the sucrose derivatives isolated after oxidation, those having a keto group in the glucopyranosyl moiety preponderated. The axial fructofuranosyl aglycon protects position 3 in the glucopyranosyl group and oxidation occurs only at C-2 and C-4. Small amounts of sucrose oxidised at C-3 in the fructofuranosyl moiety were also found. 相似文献
14.
(1) Alkyl sugar inhibition of d-allose uptake into adipocytes has been used to explore the spatial requirements of the external sugar transport site in insulin-treated cells. α-methyl and β-methyl glucosides show low affinity indicating very little space around C-1. The high affinity of d-glucosamine (Ki = 9.05 ± 0.66 mM) is lost by N-acetylation. shows no detectable affinity, indicating that a bulky group at C-2 is not accepted. Similarly (Ki = 42.1 ± 7.5 mM) has lower affinity than (Ki = 5.14 ± 0.32 mM) indicating very little space around C-2 but much more around C-3. A reduction in affinity does occur if a propyl group is introduced into the C-3 position. The Ki for is 11.26 ± 2.12 mM. (Ki = 87.2 ± 17.9 mM) and (Ki = 78.07 ± 12.6 mM) show low affinity compared with d-galactose and d-glucose, indicating steric constraints around C-6. High affinity is restored in (Ki = 4.66 ± 0.23 mM) possibly indicating a hydrophobic binding site around C-6). (2) In insulin treated cells (Ki = 6.11 ± 0.5 mM) and maltose (Ki = 23.5 ± 2.1 mM) are well accommodated by the site but trehalose shows no detectable inhibition. These results indicate that the site requires a specific orientation of the sugar as it approaches the transporter from the external solution. C-1 faces the inside while C-4 faces the external solution. (3) To determine the spatial and hydrogen bonding requirements for basal cells 40 μM was used as the substrate. Poor hydrogen bonding analogues and analogues with sterically hindering alkyl groups showed similar Ki values to those determined for insulin-treated cells. These results indicate that insulin does not change the specificity of the adipocyte transport system. 相似文献
15.
William R. Nes Kenneth Krevitz Shamideh Behzadan Glenn W. Patterson Josephine R. Landrey Robert L. Conner 《Biochemical and biophysical research communications》1975,66(4):1462-1466
The epimer of ergosterol at C-24 was formed by the metabolism of 24α-methyl-cholesterol in the protozoan, . This is the first time 24-epiergosterol has been obtained in any manner. Its n.m.r. spectrum at 220 MHz was distinguishable from that of ergosterol. From the primitive tracheophyte, L., a 24-methyl-Δ5,7,22-sterol was isolated which proved to be ergosterol possibly containing its C-24 epimer as a minor constituent. 相似文献
16.
J R Knox M L DeLucia N S Murthy J A Kelly P C Moews J M Frére J M Ghuysen 《Journal of molecular biology》1979,127(2):217-218
A pencillin-sensitive enzyme, the exocellular dd-carboxypeptidase-transpeptidase from Streptomyces R61, has been crystallized from polyethylene glycol (Mr = 6000 to 7500) solution at pH 7·6. X-ray examination of the orthorhombic crystals shows the space group is P212121, with unit cell dimensions . With four molecules of molecular weight 38,000, the ratio for the cell is 2·33. The crystals are stable to irradiation for 75 hours and are suitable for structure analysis to at least 2·4 Å resolution. The radius of gyration of the molecule in solution at pH 6.8 is 20.8 Å. 相似文献
17.
Konoshin Onodera Toshiaki Shinohara 《Bioscience, biotechnology, and biochemistry》2013,77(7):1661-1666
A simplified procedure for the purification of pea phytohemagglutinin, which involves fractionation with ammonium sulfate and column chromatography to give two active components, has been developed. The main component of the purified hemagglutinin gave one single band with disc electrophoresis. Molecular weight of the hemagglutinin was calculated as 61,000 (Vρ = 0.75). Using this hemagglutinin, the experiment was carried out to aim from the viewpoint of conformational feature of sugars at an explanation of the role of a hydroxyl group on gluco- or mannopyranoid moiety of the sugars capable of interaction with the hemagglutinin. A possible concern of orientation of hydroxyl group at the C–2 position on pyranoid moiety of sugars is proposed to interpret the hemagglutination with the phytohemagglutinin from the results of inhibition tests and from the consideration on conformational feature of sugars reported previously. 相似文献
18.
The stereospecificity of D-glucose-6-phosphate: 1L-myo-inositol-1-phosphate cycloaldolase on the hydrogen atoms at C-6 总被引:1,自引:0,他引:1
S M Byun R Jenness W P Ridley S Kirkwood 《Biochemical and biophysical research communications》1973,54(3):961-967
D-Glucose-6-phosphate: 1L--Inositol-1-phosphate cycloaldolase from rat testis or mammary gland removed stereospecifically the pro-S hydrogen atom at C-6 from D-glucose-6-phosphate. The pro-R hydrogen at C-6 remained in the product, 1L--Inositol-1-phosphate and evidence is given that it is the hydrogen at C-1 of 1L--Inositol-1-phosphate. The possible mechanism of cyclization is discussed. 相似文献
19.
Eleanor G. Rogan Alaeddin Hakam Ercole L. Cavalieri 《Chemico-biological interactions》1983,47(1):111-122
Activation of polycyclic aromatic hydrocarbons (PAH) by horseradish peroxidase (HRP) with H2O2 has been studied as a model system for one-electron oxidation. This peroxidase has been used to catalyze binding of (BP-6-CH3) to DNA, which was purified, hydrolyzed to deoxyribonucleosides and analyzed by high pressure liquid chromatography (HPLC). The predominant hydrocarbon-DNA adduct observed was identified as BP-6-CH3 bound at the 6-methyl group to the 2-amino group of dG, confirming that activation by HRP occurs by one-electron oxidation. When DNA from mouse skin treated in vivo with [14C]BP-6-CH3 was purified, hydrolyzed and analyzed by HPLC, a profile was observed which was qualitatively similar to that from the peroxidase system. In particular, the identified adduct with the hydrocarbon bound at the 6-methyl group to the 2-amino group of dG was obtained. These results demonstrate that one-electron oxidation is the mechanism of activation by HRP for aromatic hydrocarbons and indicate that the same mechanism may occur in mouse skin, a target tissue for hydrocarbon carcinogenesis. 相似文献
20.
Darwin D. Smith Scott J. Norton 《Biochemical and biophysical research communications》1980,94(4):1458-1462
Sinefungin and A9145C, antifungal antibiotic analogs of S-adeno-sylmethionine isolated from , have been found to be very effective inhibitors of cyclopropane fatty acid synthase from . Both compounds exhibit linear competitive inhibition with a Ki for Sinefungin of 220 nM and a Ki for A9145C of 11 nM. 相似文献