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81.
W. J. J. van den Tweel M. N. Widjojoatmodjo J. A. M. de Bont 《Archives of microbiology》1988,150(5):471-476
Thirteen bacteria were isolated on D-4-hydroxyphenylglycine as sole carbon and energy source. Seven strains transaminated only the D-enantiomer while the other six isolates transaminated both enantiomers of 4-hydroxyphenylglycine. One of the six strains utilizing both enantiomers was characterized as a Pseudomonas putida. This strain, MW27, employed two enantioselective transaminases, to catalyze the initial step in the metabolism of DL-4-hydroxyphenylglycine. The product of the transamination, 4-hydroxyphenylglyoxylate, was further metabolized via 4-hydroxybenzaldehyde and 4-hydroxybenzoate to protocatechuate. Preliminary results indicate that both transaminases are co-ordinately synthesized together with the 4-hydroxyphenylglyoxylate decarboxylase and the NADP+-dependent 4-hydroxybenzaldehyde dehydrogenase. 相似文献
82.
α-[3 H]Amino-3-Hydroxy-5-Methyl-4-Isoxazolepropionic Acid Binding to Rat Striatal Membranes: Effects of Selective Brain Lesions 总被引:1,自引:0,他引:1
The binding of alpha-[3H]amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid ([3H]AMPA), a structural Glu analog, to rat striatal membranes was studied. In the absence of potassium thiocyanate and Cl-/Ca2+, saturation-curve analysis of [3H]AMPA binding suggested that a single class of noninteracting binding sites with a KD value of 340 +/- 27 nM was involved, although AMPA inhibition of [3H]AMPA binding set at a concentration of 100 nM suggested, in contrast, the presence of multiple populations of striatal binding sites. Several other excitatory amino acid receptor agonists and antagonists were tested, and the most potent and selective quisqualic acid (QA) receptor agonists (QA, L-Glu, and AMPA) were found to represent the most potent inhibitors of [3H]AMPA binding. N-Methyl-D-aspartate receptor agonists and antagonists were ineffective as displacers of the [3H]AMPA binding. Lesions of intrastriatal neurons (using kainic acid local injections) and of corticostriatal afferent fibers led 2-3 weeks later to large decreases (63 and 30%, respectively) in striatal [3H]AMPA binding, whereas selective lesion of the nigrostriatal dopaminergic pathway (using nigral injection of 6-hydroxy-dopamine) was without any influence. Taken together, these results suggest that [3H]AMPA binding is primarily associated with postsynaptic intrastriatal neurons. Some [3H]AMPA binding sites may also be located presynaptically on corticostriatal nerve endings. So, in addition to the possibility that [3H]AMPA binding sites may be involved in corticostriatal synaptic transmission, it is interesting that these putative QA-preferring excitatory amino acid receptor sites may also play some role in autoregulatory processes underlying this excitatory synaptic transmission. 相似文献
83.
84.
Effects and interactions of varying CaSO4 and NaCl levels on growth and nitrogen fixation ofLeucaena leucocephala K8 were examined. Leucaena was grown in nutrient solution at four levels of CaSO4 (0.5, 1.0, 2.5 and 5.0 mM) and NaCl (1, 25, 50 and 100 mM) in randomized blocks with five replications. While NaCl significantly reduced plant growth, additions of CaSO4 increased plant height, leaf number, and biomass of salt treated plants. For the nonsaline treatments, high CaSO4 levels slightly depressed growth, which contradicts suggestions that Leucaena has a high calcium requirement. A significant
calcium/sodium interaction was not seen for nodule number or weight. Nodule number was significantly depressed by 100 mM NaCl and nodule weight of the salt stressed plants significantly increased as CaSO4 concentration increased from 0.5 to 2.5 mM. Effects of NaCl and CaSO4 on nitrogen content of plant parts were inconclusive. The promotion of Leucaena salinity tolerance by addition of CaSO4 may be attributed to the effect of calcium in maintaing the selective permeability of membranes. 相似文献
85.
Expression sites of genes encoding (13,14)--glucan 4-glucanohydrolase (EC 3.2.1.73) have been mapped in germinated barley grains (Hordeum vulgare L.) by hybridization histochemistry. A32P-labelled cDNA (copy DNA) probe was hybridized to cryosections of intact barley grains to localize complementary mRNAs. No mRNA encoding (13,14)--glucanase is detected in ungerminated grain. Expression of (13,14)--glucanase genes is first detected in the scutellum after 1 d and is confined to the epithelial layer. At this stage, no expression is apparent in the aleurone. After 2 d, levels of (13,14)--glucanase mRNA decrease in the scutellar epithelium but increase in the aleurone. In the aleurone layer, induction of (13,14)--glucanase gene expression, as measured by mRNA accumulation, progresses from the proximal to distal end of the grain as a front moving away from, and parallel to, the face of the scutellum.Abbreviations cDNA
copy DNA
- RNase
ribonuclease 相似文献
86.
Glycine decarboxylase is confined to the bundle-sheath cells of leaves of C3−C4 intermediate species
Christopher M. Hylton Stephen Rawsthorne Alison M. Smith D. Alan Jones Harold W. Woolhouse 《Planta》1988,175(4):452-459
Immunogold labelling has been used to determine the cellular distribution of glycine decarboxylase in leaves of C3, C3–C4 intermediate and C4 species in the genera Moricandia, Panicum, Flaveria and Mollugo. In the C3 species Moricandia foleyi and Panicum laxum, glycine decarboxylase was present in the mitochondria of both mesophyll and bundle-sheath cells. However, in all the C3–C4 intermediate (M. arvensis var. garamatum, M. nitens, M. sinaica, M. spinosa, M. suffruticosa, P. milioides, Flaveria floridana, F. linearis, Mollugo verticillata) and C4 (P. prionitis, F. trinervia) species studied glycine decarboxylase was present in the mitochondria of only the bundle-sheath cells. The bundle-sheath cells of all the C3–C4 intermediate species have on their centripetal faces numerous mitochondria which are larger in profile area than those in mesophyll cells and are in close association with chloroplasts and peroxisomes. Confinement of glycine decarboxylase to the bundle-sheath cells is likely to improve the potential for recapture of photorespired CO2 via the Calvin cycle and could account for the low rate of photorespiration in all C3–C4 intermediate species.Abbreviation and symbol kDa
kilodaltons
-
CO2 compensation point 相似文献
87.
Summary The relative hydraulic conductivities of major and minor longitudinal veins, and the apoplastic permeability of the bundle sheaths surrounding all longitudinal and transverse veins were investigated in representatives of the C3, C4/NAD-ME, C4/NAD-ME/PCK intermediate, C4/PCK and C4/NADP-ME photosynthetic types. Using the Hagen-Poiseuille equation and measurements of tracheary element diameters, the number of elements in each vein type and the numbers of each vein type, we calculated that 87–99% of the water flow in a longitudinal direction would be expected to occur in the major veins. The permeability of the mestome sheaths and parenchymatous bundle sheaths surrounding the veins was tested using the negatively-charged, fluorescent dye, trisodium 3-hydroxy-5,8,10-pyrenetrisulfonate (PTS). This dye proved nontoxic to plant tissue at a concentration of 0.5%, according to a deplasmolysis test with onion epidermal strips. The PTS concentration achieved in the tested grass leaves was about 0.035%, well below the toxic limit. When a solution of PTS was fed to the leaves by means of a basal cut, the dye moved into the veins of all orders. From there, it moved outward into the surrounding tissues, indicating that the sheaths surrounding the veins of all orders in all species tested were permeable. Therefore, contrary to previous predictions based on structural observations and some tracer studies, bundle sheaths with suberized cell walls do not function as endodermal layers. 相似文献
88.
The leaf ultrastructure of NADP-malic enzyme type C4 species possessing different anatomical features in the Cyperaceae was examined: types were the Rhynchosporoid type, a normal
Kranz type in which mesophyll cells are adjacent to Kranz cells, and Fimbristyloid and Chlorocyperoid types, unusual Kranz
types in which nonchlorophyllous mestome sheath intervenes between the two types of green cells. They show structural characteristics
basically similar to the NADP-malic enzyme group of C4 grasses, that is, centrifugally located chloroplasts with reduced grana and no increase of mitochondrial frequency in the
Kranz cells. However, the Kranz cell chloroplasts of the Fimbristyloid and Chlorocyperoid types exhibit convoluted thylakoid
systems and a trend of extensive development of peripheral reticulum, although those of the Rhynchosporoid type do not possess
such particular membrane systems. The suberized lamella, probably a barrier for CO2 diffusion, is present in the Kranz cell walls of the Rhynchosporoid type and in the mestome sheath cell walls of the other
two types, and tightly surrounds the Kranz cells (sheaths) that are the sites of the decarboxylation of C4 acids. These ultrastructural features are discussed in relation to C4 photosynthetic function. 相似文献
89.
Koji Sode Nobuaki Hori Yoichi Mikami Isao Karube 《Biocatalysis and Biotransformation》1988,2(1):51-57
Asymmetric reduction of 2,6,6,-trimethyl-2-cyclohexene-l,4-dione (4-oxoisophrone) to (6R)-2,2,6-trimethyl-1,4-cyclohexane-dione((3R)-dihydro-4-oxoisophorone) was catalysed by immobilized thermophilic bacteria, Thermomonospora curvata JTS 321. Because of leakage of entrapped cells from gel beads during reactions using culture medium, we optimized the medium to allow the microbial conversion under conditions of controlled cell growth. Of the media screened, liver infusion medium was found to be the most suitable and microbial conversion was achieved without cell leakage from the immobilized gels. Immobilized T. curvata cells were repeatedly used for the asymmetric reduction of 4-oxoisophorone, more than 15 times, with an extent of conversion of 50%. 相似文献
90.
马齿苋叶片PEPCase由四个相同的亚基组成,亚基分子量为83kD。远紫外CD光谱分析表明,此酶含有36.6%α—螺旋结构。马齿苋叶片PEPCase可被G6P激活,但不能被Gly、Ser激活。G6P可防止酶的尿素变性和枯草杆菌蛋白酶的作用。这种保护效应与G6P诱导的酶构象变化有关。 从酶对低温、高温及尿素的反应来看,马齿苋叶片PEPCase的稳定性高于高粱叶片PEP—Case,两者的免疫特性和电泳特性亦不同。 相似文献