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1.
Purification and characterization of a membrane-bound protein kinase from spinach thylakoids 总被引:3,自引:0,他引:3
A protein kinase was isolated from spinach thylakoid membranes by solubilization with octyl glucoside and cholate. The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, and sucrose density centrifugation, followed by affinity chromatography on either Affi-Gel blue (yielding denatured enzyme) or on histone cross-linked to Sepharose (yielding active enzyme). Electrophoresis on denaturing polyacrylamide gels, followed by staining with silver, revealed the kinase as a single band corresponding to an apparent molecular mass of 64 kDa. The active enzyme underwent autophosphorylation and could be detected by autoradiography following incubation with [gamma-32P]ATP and Mg2+ ion. The specific phosphotransferase activity of purified kinase was approximately 30 nmol of phosphate min-1 (mg protein)-1 with lysine-rich histone (III-S or V-S) as substrate; casein was phosphorylated at approximately 30% of this rate. The physiological substrate for the kinase is presumed to be light-harvesting chlorophyll a/b protein complex. In solubilized form, this was phosphorylated at approximately 10% of the rate observed with histone III-S as substrate, or 10-100 times slower than the estimated rate of phosphorylation of the light-harvesting complex in situ. Possible reasons for this shortfall are considered. The kinase is proposed as the principal effector of thylakoid protein phosphorylation and associated State transition phenomena. 相似文献
2.
Culture filtrates of Talaromyces emersonii UCG 208 grown on beet pulp can convert the polysaccharide components of this agricultural waste to soluble sugars. The saccharification process is facilitated if the pulp is milled or incubated with alkali or peracetic acid before addition of enzyme. However, treatment of unmilled pulp with commercial pectinase prior to incubation with Talaromyces filtrate is also very effective; under suitable conditions, complete hydrolysis of total polysaccharides has been achieved. 相似文献
3.
The sorption characteristics of the cellulase system of Talaromyces emersonii on various cellulosic substrates were examined. Analysis of reaction mixture supernatants by electrophoresis and enzyme assay showed that all components of the cellulase system were rapidly adsorbed by cellulose and then gradually returned to the liquid phase as the hydrolysis of the substrate progressed. The extent of adsorption in the rapid phase was influenced by pH, temperature, the nature of the substrate, and its concentration. 相似文献
4.
Turkey liver xanthine dehydrogenase. Reactivation of the cyanide-inactivated enzyme by sulphide and by selenide 下载免费PDF全文
1. The glycogen present in the liver of rat foetuses was labelled by injecting a trace amount of [6-(3)H]glucose into the mother at 19.5 days of gestation. The radioactivity incorporated in the glycogen 4h after the administration of the label was still present 38h later. A large proportion of this radioactivity was on the outer chains of the polysaccharide. These results indicate that there is normally almost no glycogen degradation in the foetal liver. In contrast, glycogen breakdown occurs very rapidly in the livers of foetuses whose mother is anaesthetized. 2. Glycogen synthetase is present in the liver at day 16 of gestation at a concentration as high as 30% of that in the adult, but essentially as an inactive (b) enzyme. The appearance of synthetase phosphatase between days 18 and 19 corresponds to that of synthetase a and to the beginning of glycogen synthesis. From day 19 to 21.5 the amount of synthetase a present in the foetal liver is just sufficient to account for the actual rate of glycogen deposition. 3. The content of total phosphorylase in the foetal liver increases continuously from day 16 to birth. However, a precise measurement of the a and b forms of the enzyme in the liver of non-anaesthetized foetuses is not possible. Taking the rate of glycogenolysis as an appropriate index of phosphorylase activity, we conclude that this enzyme is almost entirely in the inactive form in the foetal liver under normal conditions. 4. The accumulation of glycogen in the liver during late pregnancy may therefore be explained by a relatively slow rate of synthesis and a nearly total absence of degradation. 相似文献
5.
Four polymorphic microsatellites in turbot Scophthalmus maximus 总被引:2,自引:0,他引:2
6.
Recognition specificity of the duplicated segments present in Clostridium thermocellum endoglucanase CelD and in the cellulosome-integrating protein CipA. 总被引:13,自引:9,他引:4 下载免费PDF全文
S Salamitou O Raynaud M Lemaire M Coughlan P Bguin J P Aubert 《Journal of bacteriology》1994,176(10):2822-2827
The binding specificity of the duplicated segments borne by Clostridium thermocellum endoglucanase CelD and by the cellulosome-integrating protein CipA was investigated. The fusion protein CelC-DSCelD, in which the duplicated segment of CelD was fused to the COOH terminus of endoglucanase CelC, bound with an affinity of 4.7 x 10(7) M-1 to the fusion protein MalE-RDCipA, in which the seventh receptor domain of CipA was grafted onto the COOH terminus of the Escherichia coli maltose-binding protein MalE. The affinity of CelC-DSCelD for the homologous chimeric protein MalE-RDORF3p, carrying the receptor of the surface protein ORF3p, was 6.9 x 10(6) M-1. The fusion protein CelC-DSCipA, in which the duplicated segment of CipA was grafted onto the COOH terminus of CelC, did not bind detectably to MalE-RDCipA or MalE-RDORF3p. However, Western blotting (immunoblotting) experiments indicated that the duplicated segment of CipA was able to bind to a set of C. thermocellum proteins which are different from those recognized by the duplicated segment of CelD. These results argue against the hypothesis that ORF3p interacts with the duplicated segment of CipA. More probably, ORF3p binds to individual cellulases and hemicellulases harboring duplicated segments. 相似文献
7.
8.
Purine hydroxylase II from Aspergillus nidulans has been purified to near homogeneity. The enzyme has a pI of 5.7, a molecular weight of 300,000, and two subunits with molecular weight of 153,000 each. The enzyme contains 2 FAD, 2 molybdenum atoms, and 4 (2 Fe-2S) iron-sulfur centers per molecule and exhibits broad specificity for reducing and oxidizing substrates. Among the more notable characteristics are the ability to oxidize hypoxanthine and nicotinic acid but not xanthine and virtually complete inactivity with oxygen. Moreover, while the enzyme is inactivated by borate and methanol, it is very resistant to cyanide and arsenite and it not inactivated by allopurinol. At infinite concentrations of reducing and oxidizing substrates, the Km for hypoxanthine was 119 microM, for nicotinic acid was 136 microM, and for NAD+ was 525 microM. 相似文献
9.
10.