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131.
Degradation of Xyloglucan by Wall-bound Enzymes from Soybean Tissue I. Occurrence of Xyloglucan-degrading Enzymes in Soybean Cell Wall 总被引:1,自引:0,他引:1
Koyama Toru; Hayashi Takahisa; Kato Yoji; Matsuda Kazuo 《Plant & cell physiology》1981,22(7):1191-1198
An enzyme preparation that catalyzes the degradation of xyloglucanwas obtained by extraction of the cell walls of soybean hypocotylswith a buffer containing 1.0 M NaCl. The enzyme preparationwas shown to catalyze two-step degradation of xyloglucan. Thepolysaccharide was first degraded into comparatively large fragments,which were then further degraded into monosaccharides. In orderto elucidate the mode of degradation of the xyloglucan duringcell growth, the activities of xyloglucandegrading enzymes ofsoybean-hypocotyl segments were assayed at different stagesof elongation. The total activities of the degrading enzymeswere lower in the elongating regions than in the non-elongatingregions. However, high levels of endo-ß-l,4-glucanasewere found in the elongating regions. These results suggestthat xyloglucan is hydrolyzed by endo-ß-1,4-glucanaseinto comparatively large fragments at the initial stage of growthand the resulting fragments are further degraded into monosaccharidesduring cell elongation. (Received May 20, 1981; Accepted August 8, 1981) 相似文献
132.
Antisera to purified gamma-glutamyltranspeptidase (gamma GTP) from human and rat kidney were prepared, and their reactivities toward purified gamma GTP from kidney, liver, and bile were tested. The following results were obtained: 1. On double immunodiffusion, Triton-solubilized gamma GTP, and papain-solubilized gamma GTP from rat kidney gave single precipitin lines which fused completely against antiserum to the purified enzyme from rat kidney. 2. An antigen-antibody complex of human kidney gamma GTP retained about 50% of the catalytic activity of the antigen. 3. Double immunodiffusion showed that the enzymes from human liver, kidney, and bile were immunologically identical. 4. Antiserum to rat kidney gamma GTP partially cross reacted with human gamma GTP, but antiserum to human gamma GTP reacted only very weakly with rat gamma GTP. It is concluded that gamma GTP of human liver, kidney, and bile are immunologically identical and that rat gamma GTP and human gamma GTP have certain antigenic determinants in common. 相似文献
133.
134.
5-Nitro-2'-deoxyuridylate (NO2dUMP) is a potent mechanism-based inhibitor of dTMP synthetase. After formation of a reversible enzymeìnhibitor complex, there is a rapid first order loss of enzyme activity which can be protected against by the nucleotide substrate dUMP. From studies of model chemical counterparts and the NO2dUMPdTMP synthetase complex, it has been demonstrated that a covalent bond is formed between a nucleophile of the enzyme and carbon 6 of NO2dUMP. The covalent NO2dUMPènzyme complex is sufficiently stable to permit isolation on nitrocellulose membranes, and dissociates to give unchanged NO2-dUMP with a first order rate constant of 8.9 x 10(-3) min-1. Dissociation of the complex formed with [6-3H]NO2dUMP shows a large alpha-secondary isotope effect of 19%, verifying that within the covalent complex, carbon 6 of the heterocycle is sp3-hybridized. The spectral changes which accompany formation of the NO2dUMPènzyme complex support the structural assignment and, when used to tritrate the binding sites, demonstrate that 2 mol of NO2dUMP are bound/mol of dimeric enzyme. The interaction of NO2dUMP with dTMP synthetase is quite different than that of other mechanism-based inhibitors such as 5-fluoro-2'-deoxyuridylate in that it neither requires nor is facilitated by the concomitant interaction of the folate cofactor, 5,10-CH2-H4folate, and that the covalent complex formed is unstable to protein denaturants. 相似文献
135.
K Yamamoto K Itoh S Yoshida K Saito Y Sakamoto A Matsuda T Saito T Kuzuya 《Endocrinologia japonica》1979,26(2):255-261
Using B-mode ultrasonography, an attempt was made to measure the volume of extraocular muscles and retrobulbar fat in 31 patients (62 orbits) with Graves' disease. None of the patients had exophthalmometric measurements greater than 21 mm or had eye symptoms. The mean value of muscle volume of Graves' patients was significantly larger than that of normal controls (6.48 +/- 2.70 cm3 and 3.25 +/- 1.30 cm3, respectively, p less than 0.001). All of the patients had extraocular muscle swelling, although 2 of them had no extraocular muscle change for their unilateral eye. The extraocular muscle volume increased as the degree of the proptosis increased. The fat volume tended to increase in parallel with the degree of the proptosis. In the Graves' group with obvious proptosis (Hertel reading: 19--21 mm), the fat volume increased more significantly than in any other group. The ratio of extraocular muscle volume to retrobulbar fat volume was significantly higher in Graves' disease, but it did not increase as the degree of the proptosis increased. A significant correlation between proptosis and muscle volume plus fat volume was observed. No significant difference of the extraocular muscle volume was observed between the patients untreated and treated with antithyroid drugs. The data show a uniform enlargement of the extraocular muscles in Graves' disease and also suggest an involvement of increased retrobulbar fat volume in a group of obvious exophthalmos. The degree of the proptosis is in aclose proportion ot the quantitative change of the orbital soft tissue. 相似文献
136.
137.
G Matsuda T Maita Y Suzuyama M Setoguchi T Umegane 《Hoppe-Seyler's Zeitschrift für physiologische Chemie》1978,359(5):629-640
The amino acid sequences of the tryptic peptides from the aminoethylated L-2 light chain of rabbit skeletal muscle myosin were determined by various enzymatic hydrolyses, partial hydrolysis with dilute acetic acid and Edman degradation. The amino acid sequences of the chymotryptic and peptic peptides from the carboxymethylated L-2 light chain were partially analysed in the same manner as the tryptic peptides. The primary structure of the L-2 light chain of rabbit skeletal muscle myosin was deduced from the above results. 相似文献
138.
Coumarin, a specific inhibitor of the biosynthesis of celluloseof higher plant cell walls, inhibited the cellulose formationof Acetobacter xylinum. The degree of inhibition reached 55%in the presence of 1 mM coumarin, which causes 70% inhibitionin the case of plant cellulose. (Received April 12, 1976; ) 相似文献
139.
A small amount of cytoplasmic ß-1,4-glucan, whichmight be involved in the synthesis of cellulose in the cellwall, was found in the homogenate prepared from the hypocotylsof seedlings of Phaseolus aureus. Upon hydrolysis by cellulaseof the 20,000?g pellet from the cytoplasmic fraction of segmentsincubated in a [14C]-glucose solution, [14C]-cellobiose wasproduced, with specific radioactivities 3 to 10 times greaterthan those of the cellobiose from cellulose in the cell wallat various incubation periods. The incoporation of radioactivityfrom [14C]-glucose into this cytoplasmic ß-1,4-glucanwas therefore faster than that into cellulose constituting thecell wall. Hence, it seemed that the former ß-1,4-glucancould be turned over. To examine whether the- cytoplasmic ß-1,4-glucanis carried by some subcellular components, cytoplasmic ß-1,4-glucanin the cell was fractionated by differential centrifugation,two enzyme activities being measured as the markers of subcellularcomponents. The distribution of ß-1,4-glucan was similarto that of UDPG-glucosyltransferase activity but not to thatof IDP-ase activity. The result suggests that the cytoplasmicß-1,4-glucan has some relation to plasma membranes. Coumarin, known as a specific inhibitor for the biosynthesisof cellulose in plant cells, was shown to inhibit the incorporationof radiocarbon from [14C]-glucose into cytoplasmic ß-1,4-glucanto the same extent as that into cellulose in the cell wall ofthe hypocotyls.
1 Present address: Department of Biological Science, TohokuUniversity, Kawauchi, Sendai 980, Japan. (Received May 31, 1976; ) 相似文献
140.
The non-cellulosic ß-glucan1 in the cell wall of Phaseolusaureus hypocotyb was studied. Evidence that xyloglucan is presentin a hemicellulose fraction was obtained by its isolation fromcell wall preparations. This polysaccharide was homogeneouson zone electrophoresis and ultracentrifugation. On acid hydrolysis,it gave glucose, xylose, galactose, and fucose in the approximatemolar ratio of 10 : 7 : 2.5 : 1. Its solution gave a reddishviolet color with iodine-staining solution. The results of partialacid hydrolysis and cellulase treatment suggest a structurein which xylose, galactose, and fucose attached as side chainsto a sequenceof ß-l,4-linked glucose. The xyloglucanisolated accounted for 13.9% of the total non-cellulosic fractions. (Received May 10, 1976; ) 相似文献