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1.
The first compound in the series of reactions leading to the ester conjugates of indole-3-acetic acid (IAA) in kernels of Zea mays sweet corn is the acyl alkyl acetal, 1-O-indol-3-ylacetyl-β-d-glucose (1-O-IAGlu). The enzyme catalyzing the synthesis of this compound is UDP-glucose:indol-3-ylacetate glucosyl-transferase (IAGlu synthase). The IAA moiety of the high energy compound 1-O-IAGlu may be enzymatically transferred to myo-inositol or to glycerol or the 1-O-IAGlu may be enzymatically hydrolyzed. Alternatively, nonenzymatic acyl migration may occur to yield the 2-O, 4-O, and 6-O esters of IAA and glucose. The 4-O and 6-O esters may then be enzymatically hydrolyzed to yield free IAA and glucose. This work reports new enzymatic activities, the transfer of IAA from 1-O-IAGlu to glycerol, and the enzymecatalyzed hydrolysis of 4-O- and 6-O-IAGlu. Data is also presented on the rate of non-enzymatic acyl migration of IAA from the 1-O to the 4-O and 6-O positions of glucose. We also report that enzymes catalyzing the synthesis of 1-O-IAGlu and the hydrolysis of 1-O, 4-O, and 6-O-IAGlu fractionate as a hormone metabolizing complex. The association of synthetic and hydrolytic capabilities in enzymes which cofractionate may have physiological significance. 相似文献
2.
Steffen Strcller Stanislaw Karpinski Jan-Erik Hällgren Gunnar Wingsle 《Physiologia plantarum》1994,92(3):443-450
A differential analysis of CuZn-superoxide dismutase (SOD. EC 1.15.1.1) isozymes after native-polyacry lamide gel elecrrophoresis (PAGE) and isoelectric focusing (IEF) indicated that germinating seeds of Scots pine (Pinus sylvestris L.) 3 days after the start of imbibition (3 DAI) contain five CuZn-SOD isozymes. Two isozymes co-migrated on native–PAGE but were separated after IEF. CuZn-SODs of Scots pine were purified from germinating seeds (3 DAI) by anion-exchange chromatography, hydrophobic interaction chromatography and chromatofocusing. The final separation of CuZn-SOD isozymes was accomplished by native-PAGE. CuZn-SOD isozymes were electroblotted and their NH2 -terminal amino acid sequence was determined. Comparisons of the amino acid sequences with sequences of CuZn-SOD isozymes from other plant sources indicated that one CuZn-SOD isozyme was of the chloroplastic type whereas the other four isozymes belonged to the cytosolic-type CuZn-SODs, The NH2 -terminal amino acid sequence of the chloroplastic CuZn-SOD and of one cytosolic-type CuZn-SOD were identical to those of two previously isolated, sequenced and localized CuZn-SOD isozymes from Scots pine needles. Two cytosolic-type CuZn-SOD isozymes showed a homology at 20 out of 21 NH2 -terminal amino acids. Mitochondria and glyoxysomes were isolated by differential and Percoll density-gradient centrifugation from germinating seeds (3 DAI). The cell fractionation experiments did not suggest that a major part of the CuZn-SOD activity in germinating seeds was derived from glyoxysomes or mitochondria. 相似文献
3.
Summary The total amount of novel oligosaccharides synthesized by -D-fructofuranosidase at pH 7.5 increased three-fold using a medium composed of 1.2M sucrose, 0.5M fructose and 0.1M glucose, as compared to that with only 1.8M sucrose solution. Using 0.6M of the three sugars did not increase yield but reduced rate of sucrose hydrolysis by 72.7%. Synthesis of fructosyl/glucosyl oligosaccharides based on -fructofuranosidase mediated transglycosylation is enhanced by supplementation of sucrose solution with appropriate concentrations fructose and glucose. 相似文献
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Summary Human fibroblasts and HeLa cells were treated with bunaftine (N-butyl-N-/2-(diethylamino)ethyl/-1-naphthalenecarboxamide) in vitro. At concentrations of 0.5–2.0 mM, the drug caused contraction and rounding of the cells with loss of microvilli-like processes. Aggregates of dense, partly granular, partly fibrillar material formed in the cytoplasm and the rough endoplasmic reticulum became vesiculated. Immunofiuorescence microscopy with DNase I and anti-DNase I demonstrated that bundles of actin filaments were disrupted, forming rings, coils, and granules. Filaments stained with antibodies to vimentin (fibroblasts) and prekeratin (HeLa cells) showed less characteristic rearrangements, probably related to the rounding up of the cells. 0.4 mM bunaftine increased and 0.8–1.0 mM markedly decreased the percentage of mitotic cells, without accumulation of cells in any particular stage of mitosis. The drug may arrest the cell cycle at some point before mitosis; it may have a critical concentration above which the arrest becomes permanent.These results suggest that bunaftine interferes with the integrity of microfilament bundles in a different manner from that of cytochalasins. It does not cause any depletion of cellular ATP, indicating that its effect is not a result of inhibition of cell metabolism. It is proposed that bunaftine may be used as a complement to cytochalasins in studies of the microfilament system of the cell. The possible binding of bunaftine to actin or myosin and further details of its mechanism of action remain to be elucidated. 相似文献
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Stanislaw Ulaszewski Elisabetta Balzi André Goffeau 《Molecular & general genetics : MGG》1987,207(1):38-46
Summary In the yeast Saccharomyces cerevisiae, the pma1 mutations confers vanadate-resistance to H+-ATPase activity when measured in isolated plasma membranes. In vivo, the growth of pma1 mutants is resistant to Dio-9, ethidium bromide and guanidine derivatives. This phenotype was used to man the pma1 mutation adjacent to LEU1 gene on chromosome VII. From a cosmid library of a wild-type Saccharomyces cerevisiae genome, a large 30 kb DNA fragment was isolated by complementation of a leu1-pma1 double mutant. A 5 kb HindIII fragment was subcloned and it restored both Leu+ and Pma+ phenotypes after integrative transformation. The restriction map of the 5 kb HindIII fragment and Southern blot analysis reveal that the cloned fragment contains the entire structural gene for the plasma membrane ATPase and the 5 end of the adjacent LEU1 gene. The pma1 mutation conferring vanadate-resistance is thus located in the structural gene for the plasma membrane ATPase.Publication no 2456 from the Biology Directorate of the Commission of European Communities 相似文献
9.
Cyanide controls enzymes involved in lipid and sugar catabolism in dormant apple embryos during culture 总被引:1,自引:0,他引:1
The activities of alkaline lipase (EC 3.1.1.3, AlkL), isocitrate lyase (EC 4.1.3.1. ICL), pyruvate kinase (EC 2.7.1.40. PK) and glucose–6–phosphate dehydrogenase (EC 1.1.1.49, G6PDH) were determined in cultured, dormant embryos of apple (Malus domestica Borb. cv. Antonówka), pretreated with gaseous HCN. The C6 /C1 , ratio was estimated in the same material. The activities of AlkL and ICL were not stimulated by HCN pretreatment until the period of maximum stimulation of germination. The activity of G6PDH was inhibited by cyanide only late during the culture of embryos. Therefore, the changes in these activities are considered to be the result and not the cause of enhanced germination. On the other hand, also PK, active very early during the culture of embryos, was modified as a result of the treatment. The cyanide-induced changes in activity of this enzyme in cotyledons (inhibition followed by stimulation) were similar to those in the whole embryo, whereas its changes in the embryonal axis (stimulation followed by inhibition) resembled CN-induced changes in PK in axes of apple seeds submitted to cold stratification (Bogatek and Lewak 1988). The estimation of C6 /C1 ratios partly confirmed these observations. A role of HCN-induced modifications of PK activity in embryonal dormancy is proposed. 相似文献
10.
Stanislaw Baranski Z. Edelwejn M. Wojtkowiak 《Origins of life and evolution of the biosphere》1970,2(3):400-403
A series of experimental investigations are described concerning the influence of hypokinesia, acceleration and associated effect of hypokinesia and acceleration in different periods of time on the displacement of plasma proteins and on bioelectric activity of striated muscles. Disturbances in hemodynamic and bioelectric activity of striated muscles by these two factors are discussed. 相似文献