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Involvement of NADPH-cytochrome c reductase in the rat liver squalene epoxidase system

Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism 1977年第3期486卷 401-407页

作者： Teruo, Ono Shigeru, Ozasa fumihiko, Hasegawa Yoh, Imai Department of Biochemistry School of Medicine Hokkaido University Sapporo 060 Japan

Microsomal squalene epoxidase has previously been solubilized with Triton X-100 and resolved into fractions, fA and fB, by DEAE-cellulose chromatography (Ono T. and Bloch K. (1975) J. Biol. Chem. 250, 1571-1579). It h... 详细信息

Microsomal squalene epoxidase has previously been solubilized with Triton X-100 and resolved into fractions, f_A and f_B, by DEAE-cellulose chromatography (Ono T. and Bloch K. (1975) J. Biol. Chem. 250, 1571-1579). It has now been found that f_B is identical with NADPH-cytochrome c reductase (denoted f_PT, EC 1.6.2.3). Although both NADPH and NADH served as electron donors, the former was preferred for squalene epoxidase activity in the reconstituted system of f_A and f_B. f_B is characterized by its ability to reduce cytochrome c by NADPH. In place of f_B, partially purified f_PT was tested for its ability to support squalene epoxidation in the presence of f_A. A stepwise purification of the deoxycholate-solubilized f_PT yielded an increase in specific f_PT activity with a parallel increase in squalene epoxidase activity. Bromelain-solubilized f_PT was less effective. Rabbit antisera preparations to the purified f_PT solubilized with trypsin were shown to inhibit concomitantly f_PT. activity and squalene epoxidase activity. These observations support the concept that squalene epoxidation is primarily mediated via a flavoprotein, NADPH-cytochrome c reductase, and a terminal oxidase, squalene epoxidase, which is distinct from cytochrome P-450. © 1977.

关键词： f A squalene epoxidase fraction A f B squalene epoxidase fraction B f PT NADPH-cytochrome c reduetase anti-f PT antibody to NADPH-cytochrome c reductase

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SHORT-TERM PHYTOCHROME RESPONSE IN SEED-GERMINATION

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ZEITSCHRIfT fUR PfLANZENPHYSIOLOGIE 1977年第5期85卷 445-450页

作者： HAUPT, W SCHEUERLEIN, R Institut für Botanik and Pharmazeutische Biologie der Universität Erlangen-Nürnberg

The germination of the photoblastic seeds of Lactuca sativa can be induced by a red flash in the millisecond range already. The induction is given either by one single flash or by two flashes, separated by a dark interval of 20 s, the total energy being equal under both these conditions. Dose response curves for single and double flash experiments differ very little from each other, but the saturation level is significantly higher in the double flash experiments. However, the effect of continuous irradiation of 20 s and longer saturates at a still higher level. We suggest to consider dark reactions of phytochrome intermediates as being responsible for the observed results.

关键词： phytochrome seed germination short-term effect intermediates R red λ max , ca. 650 nm fR far-red, 700 nm P r , P f phytochrome in the red absorbing and in the far-red absorbing form, respectively

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Evaluation of steam generator designs for application to the 300-MW(e) gas-cooled fast breeder reactor

Evaluation of steam generator designs for application to the...

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作者： Baroczy, C. J. General Atomics San Diego CA (United States)

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DIPHASIC TRANSfORMATIONS Of f-ACTIN - EffECTS Of UREA AND MGCL-2 ON f-ACTIN

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BIOCHIMICA ET BIOPHYSICA ACTA 1976年第1期427卷 126-140页

作者： TANIGUCHI, M NAGOYA UNIV FAC SCIDEPT PHYSNAGOYA 464JAPAN

Asakura, Taniguchi and Oosawa [1] proposed that muscle actin polymer under sonic vibration is in a different state from that of the ordinary double stranded helical structure (f-actin), characterised by partially interrupted structures of f-actin, a state of “f-actin”. In order to confirm different states for actin polymers [1, 2], physicochemical studies were made by measurements of viscosity, flow birefringence, electric birefringence, fluorescence, electron microscopy, quasielastic light scattering and ATP splitting. The following results were obtained. 1. (1) f-actin polymers can undergo two processes of depolymerization upon treatment with urea and various salts as judged by measurements of flow birefringence and viscosity: one is a rapid process in a solution containing K 1 or Ca 2+ and urea; the other is a slow process following a brief rapid one in a solution containing Mg 2+ and urea. 2. (2) In the presence of Mg 2+ and a suitable concentration of urea, f-actin (f mu -actin) appeared to exhibit different properties than ordinary f-actin; it had lower viscosity and lower flow birefringence and it had on the whole a more flexible polymer structure, also judging from experiments of quasielastic light scattering, electric birefringence. The different structure was confirmed directly by electron microscopic observation. The aromatic side chains of f mu -actin were also more mobile than those of f-actin judging from fluorescence measurements. The transformation between f-actin and f mu -actin was reversible. 3. (3) The state of f mu -actin polymers was also characterized by ATP splitting; f mu -actin split about one mole of ATP into ADP and inorganic phosphate per mole of actin monomer at room temperature, where f-actin did not. A molar excess of Mg 2+ with respect to actin monomer is required for ATP splitting. f-actin in solutions containing K + or Ca 2+ and urea did not split ATP. f mu -actin activated on Mg•ATPase of myosin at nearly the same rate as that of

关键词： f mu -actin in a solvent of 60 mM KCl 10 mM Tris•HCl buffer (pH 8.3) 0.4 mM ATP 2–3 mM MgCl 2 and 2 M < urea concentration < 4 M

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N-TERMINAL AMINO-ACID SEQUENCE Of CYTOCHROME-f fROM SPIRULINA-PLATENSIS

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PHYTOCHEMISTRY 1976年第5期15卷 815-816页

作者： SANDERSON, S HASLETT, BG BOULTER, D UNIV DURHAM DEPT BOTDURHAM DH1 3LEENGLAND

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f=15M~2自动板框压滤机试制技术小结

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江苏化工 1976年第4期 33-37页

一、概况过滤在化工生产中是普遍应用的化工过程之一,用于固、液两相分离。由于分离的推动力不同,分为吸滤,加压过滤和离心分离三类。而目前生产中,对于粘性较大难过滤的物料,必须加压过滤,即需较大的推动才能过滤。在加压过滤设备中,... 详细信息

一、概况过滤在化工生产中是普遍应用的化工过程之一,用于固、液两相分离。由于分离的推动力不同,分为吸滤,加压过滤和离心分离三类。而目前生产中,对于粘性较大难过滤的物料,必须加压过滤,即需较大的推动才能过滤。在加压过滤设备中,到现在极大部分仍沿用板框压滤机,这种老式板框压滤机在板框的压紧、拉开,卸料和洗刷滤布方面都是采用落后的手工操作,不仅操作工人的劳动强度大,生产条件恶劣,而且劳动生产率很低,严重地影响我国染化、制药等化工行业的生产大幅度发展。为了填补我

关键词：板框压滤机 f=15M~2 滤布过滤织物工业用织物 f 技术小结

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EffECT Of MERCURIC AND SILVER IONS ON CESIUM-SULfATE EQUILIBRIUM BUOYANT DENSITIES Of SYNTHETIC POLYDEOXYRIBONUCLEOTIDES

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BIOCHIMICA ET BIOPHYSICA ACTA 1976年第3期425卷 265-277页

作者： LIEBERMAN, MW HARVAN, DJ AMACHER, DE PATTERSON, JB NIEHS ENVIRONM MUTAGENESIS BRANCH SOMATIC CELL GENET SECT RESEARCH TRIANGLE PK NC 27709 USA

The effect of Hg 2+ and Ag + on the buoyant density (ϱ) of four synthetic DNA polymers, poly[d(A-T)]; poly(dA) · poly(dT); poly[d(G-C)]; and poly(dG) · poly(dC), was investigated. The buoyant density of poly[d(A-T)] in Cs 2 SO 4 increased dramatically after complexing with Hg 2+ , but little change in the buoyant density of other polymers resulted except at very high molar ratios of Hg 2+ DNA -P ( r f ) Hg 2+ raised the thermal transition temperature ( T m ) of alternating polymers and lowered the T m of homopolymers. Measurements in the preparative ultracentrifuge indicated that lowered T m correlated with Hg 2+ -induced strand separation of one homopolymer [poly(dA) · poly(dT)], but strand separation was not observed with another homopolymer [poly(dG) · poly(dC)] complexed with Hg 2+ . When Ag + was mixed with the polymers, the buoyant density of poly(dG) · poly(dC) increased most markedly. A substantial increase in the buoyant density of poly[d(A-T)] and a small increase in the buoyant density of poly[d(G-C)] were also observed. The T m changes induced by Ag + were not related in any obvious way to buoyant density changes. These findings indicate that nucleotide sequence as well as overall base composition is of importance in understanding the buoyant density changes induced by metal ions. Although these data do not allow construction of a detailed molecular model of polymer-metal ion interactions, they may be used to explain much of the behavior of naturally occurring DNA sequences, such as heterochromatic satellite sequences and 5 S and rRNA sequences, in Hg 2+ /Cs 2 SO 4 and Ag + /Cs 2 SO 4 gradients.

关键词： r f value the molar ratio of metal ions to DNA-phosphate

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RECIPROCAL INTERACTIONS Of PROGESTERONE AND 17ALPHA-OH-PROGESTERONE AS EXOGENOUS SUBSTRATES Of RAT ADRENAL 21-HYDROXYLASE

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JOURNAL Of STEROID BIOCHEMISTRY AND MOLECULAR BIOLOGY 1976年第10期7卷 761-767页

作者： ORTAfLORES, Z CANTU, JM DOMINGUEZ, OV INST MEXICANO SEGURO SOCIAL RES DEPT EXPTL MED DIV BIOCHEM Mexico City 73 MEXICO INST MEXICANO SEGURO SOCIAL RES DEPT EXPTL MED GENET SECT Mexico City 73 MEXICO

Due to the small concentration and activity of adrenal ***.-hydroxylase, the main corticoids secreted in the rat are DOC, Bk,Ak, 18-OH-DOC [cortexone, corticosterone, 21-hydroxy-4-pregnene-3,11,20-trione and 18-hydroxy-cortexone, respectively] and aldosterone, formed directly from progesterone (I). Because of the limited amounts of ***.-OH-progesterone (II) available, biosynthesis of SR [17,21-dihydroxy-4-pregnene-3,20-dione] fk [cortisol) and Ek [cortisone] is restricted. Since 21-OH steroid hydroxylase (21-OH-ase) uses both I and II in corticoid biosynthesis in other species, it was of interest to study the comparative interactions which could exist between these 2 precursors and rat adrenal 21-OH-ase, determining enzymatic constants for I and II (usual and unusual substrates, respectively). Homogenized adrenals from normal rats were incubated with various combinations of concentrations of 3H-I and/or 14C-II, acting as substrates and/or inhibitors of 21-OH-ase. 21-OH-ase uses II almost as efficiently as I. Km values were about the same for both I and II (13.9 and 14.2 .times. 10-6 M, respectively);however, Vmax values were 54.6 and 26.0 .times. 10-7 M/min for I and II, respectively. Amounts of I required to saturate the 21-OH-ase was double that of II. Both I and II inhibit the 21-hydroxylation of the other in a reciprocal fashion. While II inhibits the 21-hydroxylation of I by competitive inhibition, I inhibits the 21-hydroxylation of II through a mixed type of inhibition. Rather than the existence of 2 different specific enzymes (one for I and another for II) as has been postulated by others, there is probably a 21-hydroxylation system with 2 active sites. One site used only I, and the other site uses I and/or II indistinctively.

关键词： P Progesterone Progesterone 4-Pregene-3,20-dione 17-OH-P 17α-hydroxyprogesterone 17α-hydroxyprogesterone 17α-hydroxy-4-Pregnene-3,20-dione DOC Cortexone Cortexone 21-hydroxy-4-Pregnene-3,20-dione B k Corticosterone Corticosterone 11β,21-dihydroxy-4-pregnene-3,20-dione Aldo Aldosterone Aldosterone 11β,21-dihydroxy-4-pregnene-18-al-3,20-dione f k Cortisol Cortisol 11β,17α,21-trihydroxy-4-pregnene-3,20-dione S R Substance's Reichstem S Substance's Reichstem S Cortexolone Cortexolone 17,21-dihydroxy-4-pregnene-3,20-dione 18-OH-DOC 18-hydroxy-DOC 18-hydroxy-DOC 18,21-dihydroxy-4-pregnene-3,20-dione E k Cortisone Cortisone 17,21-dihydroxy-4-pregnene-3,11,20-trione A k Kendall's Compound A Kendall's Compound A 21-hydroxy-4-pregnene-3,11,20-trione 17α-OH-ase 17α-hydroxylase 21-OH-ase 21-hydroxylase 11β-OH-ase 11β-hydroxylase

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fUNCTION Of PLASTOQUINONE AS ELECTRON AND PROTON CARRIER IN PHOTOSYNTHESIS

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BIOELECTROCHEMISTRY AND BIOENERGETICS 1976年第2期3卷 302-318页

作者： SIGGEL, U TECH UNIV BERLIN MAX VOLMER INSTD-1000 BERLIN 10FED REP GER

The aim of this paper is to compile earlier and recent experimental results by flash photometry in order to discuss the possible mechanisms of coupled proton and electron transport by the plastoquinone system. The results from different techniques ( e.g. fluorescence studies) which sometimes lead to different conclusions are not included.

关键词： AH proton translocator molecule of unknown identity Chl- a 1 and Chl- a II reaction centre chlorophylls of photosystem I and II respectively Cyt- f cytochrome f DCMU 3-(3 4-dichlorophenyl)-I I-dimethylurea MES 2-(N-morpholino)-ethanesulfonate PCy plastocyanine PQ plastoquinone PQH 2 plastohydroquinone PQH . plastosemiquinone PQ .− plastosemiquinone-anion PQ o sum of these 4 species Tricine N-tris (hydroxymethyl)methylglycine U direct acceptor for the electrons of the PQ-pool (mainly PCy) X special plastoquinone not included in the pool X − special plastosemiquinone-anion X 2 2− twin of two X − X 2 o sum of twins of X − and X Y primary electron donor of light reaction II Z primary electron acceptor of light reaction I

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CHOLINE KINASE KINETIC STUDIES - DUAL ROLE Of MG2+ IN SEQUENTIAL ORDERED MECHANISM AT LOW REACTANT CONCENTRATIONS - REGULATORY IMPLICATIONS

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INTERNATIONAL JOURNAL Of BIOCHEMISTRY 1976年第9-10期7卷 483-496页

作者： INfANTE, JP KINSELLA, JE CORNELL UNIV COLL AGR & LIFE SCIITHACANY 14853

The kinetics of the forward reaction catalyzed by choline kinase from rat liver was studied at pH 8.0. The enzyme follows 2 alternative mechanisms according to the concentrations of reactants. Studies at low ligand concentrations are consistent with a sequential order mechanism with the reactants adding in the order: choline, MgATP −2 and Mg 2+ ∗ The apparent and true values of the corresponding kinetic parameters are reported. The possible implications of the dual role of Mg 2+ on the regulation of the activity of this enzyme are discussed.

关键词： [Mg 2+ ] f free Mg 2+ concentration [ATP] i total ATP concentration [Mg 2+ ] i total Mg 2+ concentration [ATP] f free ATP concentration choline kinase or ATP choline phosphoryl transferase (EC 2.7.1.32)

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