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1.
2- Cis (-)xanthoxin (XA) was linked to bovine serum albumin through a Schiff's base and the adduct stabilized by sodium borohydride reduction. The conjugate (molar coupling ratio: 3 mol XA per mol protein) was highly immunogenic in rabbits. Antisera contained antibodies binding XA with high affinity (Ka= 1.8 × 108 M −1). [3H]-XA (2.2 × 1014 Bq mol−1) was synthesized by oxidation of [3H]-XA alcohol with MnO2 and used to set up a radioimmunoassay [RIA, detection limit, 1 pmol; measuring range, 1 to 200 pmol (0.3 to 60 ng) XA]. The sera were also suitable for enzyme-linked-immunosorbent assay (ELISA) using XA-alkaline phosphatase conjugates. The technique was more sensitive [detection limit, 0.1 pmol; measuring range, 0.1 to 50 pmol (0.05 to 15 ng) XA] than the radioimmunoassay, but less precise.  相似文献   

2.
Abstract In Zymomonas mobilis a novel pathway for the formation of glycerol 3-phosphate was identified by enzymatic studies and nuclear magnetic resonance spectroscopy. This pathway branches off from the Entner-Doudoroff pathway at the intermediate glyceraldehyde 3-phosphate and proceedes via dihydroxyacetone phosphate, dihydroxyacetone, glycerol to glycerol 3-phosphate. The reaction sequence is catalyzed by the enzymes triosephosphate isomerase (0.4 U (mg protein)−1), dihydroxyacetone phosphatase (0.31 U (mg protein)−1), dihydroxyacetone reductase (0.25 U (mg protein)−1), and glycerokinase (0.08 mU (mg protein)−1), respectively. The action of a postulated aldolase catalyzing the cleavage of fructose 6-phosphate to dihydroxyacetone and glyceraldehyde 3-phosphate could be excluded.  相似文献   

3.
Abstract Suspensions of maltose-grown cells of the hyperthermophilic archaeon Pyrococcus furiosus , when incubated at 90°C with 35 mM [1-13C]glucose or [3-13C]glucose, consumed glucose at a rate of about 10 nmol min−1 (mg protein)−1. Acetate (10 mM), alanine (3 mM), CO2 and H2 were the fermentation products. The 13C-labelling pattern in alamine and acetate were analyzed. With [1-13C]glucose the methyl group of both alanine and acetate was labelled; with [3-13C]glucose only the carboxyl group of alanine was labelled whereas acetate was unlabelled. Extracts of maltose-grown cells contained glucose isomerase (12.8 U mg−1, 100°C), ketohexokinase (0.23 U mg−1, 100°C), and fructose 1-phosphate aldolase (0.06 U mg−1, 100°C). Enzymes catalyzing the formation of fructose 1,6-bisphosphate from fructose 1-phosphate or fructose 6-phosphate could not be detected. As publihed previously by our group and other authors P. furiosus also contains enzymes of glyceraldehyde conversion to 2-phosphoglycerate according to a non-phosphorylated Entner-Doudoroff pathway, of dihydroxyacetone phosphate conversion to 2-phosphoglycerate according to the Embden-Meyerhof pathway, and of 2-phosphoglycerate conversion - via pyruvate - to acetate and alanine. Based on the enzyme activities in P. furiosus , the following pathway for glucose degradation to alanine and acetate in cell suspensions is proposed which can explain the [13C]glucose labelling data: glucose→ fructose → fructose 1- phosphate → dihydroxyacetone phosphate + glyceraldehyde and further conversion of both trioses to alanine and acetate via pyruvate.  相似文献   

4.
Aromatic L-amino acid decarboxylase activity was measured in brain, heart, intestine, kidney, liver, muscle, pyloric caeca, spleen and stomach of skipjack, using L-3,4–dihydroxyphenylalanine as the substrate. Aromatic L-amino acid decarboxylase activity was found to be present in all of the organs studied. The highest activity was found in the intestine (1774 μmol min −1 g−1 wet wt of tissue). The liver showed the lowest activity (48.7 umol min −1 g −1).  相似文献   

5.
Abstract— Uptake and release of glutamine were measured in primary cultures of astrocytes together with the activity of the phosphate activated glutaminase (EC 3.5.1.2). In contrast to previous findings of an effective, high affinity uptake of other amino acids (e.g. glutamate, GABA) no such uptake of glutamine was observed, though a saturable, concentrative uptake mechanism did exist (K m = 3.3 ± 0.5 m m ; V max= 50.2 ± 12.6 nmol ± min−1± mg−1). The phosphate activated glutaminase activity in the astrocytes (6.9 ± 0.9 nmol ± min−1± mg−1) was similar to the activity found in whole brain (5.4 ± 0.7 nmol ± min −l± mg−1), which may contrast with previous findings of a higher activity of the glutamine synthetase (EC 6.3.1.2) in astrocytes than in whole brain. The observations are compatible with the hypothesis of an in vivo flow of glutamate (and GABA) from neurons to astrocytes where it is taken up and metabolized, and a compensatory flow of glutamine towards neurons and away from astrocytes although the latter cell type may be more deeply involved in glutamine metabolism than envisaged in the hypothesis.  相似文献   

6.
During the auxin-sensitive phase of root initiation, rates of 3-indolyl- [2-14C] acetic acid (IAA) uptake into the 1 cm bases of shoots of the apple rootstock M.9 ( Malus pumila Mill.) 'in vitro' were not significantly affected by the presence of 10−3 M phloroglucinol (PG) using either liquid or agar-solidified media. The use of a liquid medium did however reduce rates of uptake over a 10-day period of auxin application. The distribution of labelled IAA between the 1-cm base and the shoot remainder was not affected by PG.
Exposure of shoots of the difficult-to-root M.9 and the easy-to-root M.26, to 2.8 × 10−5 M IAA containing [2-14C] IAA revealed no positive correlation between the amount of label taken up by the 1-cm base and rooting performance. M.9 bases absorbed almost twice as much label as M.26 after 9 days but had produced only one-third as many roots. Measurements of label distribution between the 1-cm base and the shoot remainder showed that less than 10% of the label moved to the shoot remainder over a 6-day period of auxin application. Dose-response curves of IAA and rooting over the range 1 × 10−5 M and 3 × 10−3 M showed that root number in M.9 was at an optimum at 1 × 10−3 M IAA after 6 days whilst M.26 required only 1 × 10−4 M for a similar response. These data support the hypothesis that differences in rooting of the two rootstocks reflect differences in the endogenous metabolism of exogenous IAA and not differences in its rates of uptake or distribution in the shoots.  相似文献   

7.
In vitro shoots of cv. Doyenne ďHiver pear ( Pyrus communis L.) were irradiated under controlled environments for 6 h per day at 5 different levels of biologically effective UV-B radiation (UV-BBE). UV-B exposure caused a progressive increase in apical necrosis above background levels and stimulated leaf abscission. Shoots grown for 2 weeks at 7. 8 mol m−2 day −1 of photosynthetic photon flux (PPF) and treated with 8. 4 or 12. 0 kJ m−2 day −1 UV-BBE produced up to 4 times more ethylene than those given 2. 2 or 5. 1 kJ m−2 day−1 UV-BBE or untreated controls. Exposure of shoots to 12 kJ m−2 day −1 of UV-BBE caused an increase in free putreseine content after 4 to 14 days of irradiation. Shoots showed a decrease in CO2 uptake after 3 days of UV-B: thereafter, they appeared to recover their photosynthetic capacity. Under typical PPF conditions used in micropropagation (90 μmol m−2 S−1). 8. 4 kJ m−2 day −1 of UV-B radiation was injurious to realatively tender tissues of in vitro pear shoots: increasing the level of UV-BBE to 12 kJ m−2 day−1 produced even more adverse effects.  相似文献   

8.
Abstract: The direct influence of l -3,3',5-triiodothyronine (T3) on the development of 2',3'-cyclic nucleotide 3'-phosphohydrolase (EC 3.1.4.37, CNPase) is demonstrated by using an in vitro culture system of dissociated embryonic mouse brain cells. Serum from a thyroidectomized calf, which contained low levels of T3 (31 ng/100 ml), and thyroxine, T4 (<1 μg/ml), was used in the culture medium in place of normal calf serum (T3, 103 ng/100 ml; T4, 5.7 μg/ml) to render the culture responsive to exogenously added T3. The lower levels of enzyme activity observed in the presence of such a deficient medium could be restored to normal values by T3 supplementation. Half-maximal effect was obtained with 2.5 ± 10−9 m -T3. Three days of hormone treatment resulted in the maximal stimulation of CNPase. T4 was less effective in inducing CNPase activity and the inactive analog of the hormone, reverse T3 (3,3',5'-T3) was ineffective. The morphological appearance of the cells was characterized by deformed (smaller size and less in number) reaggregates in the cultures, lacking hormone.  相似文献   

9.
Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O2 larva−1 h−1, of older yolk sac larvae 10.09 μl O2 larva−1 h−1, and of one-month-old fry 32.99 μl O2 larva−1 h−1. The QO2 values showed a decrease with development and growth, ranging from 21.2–26.0 μl O2 mg−1 h−1 in newly hatched larvae to 2.97 μl mg−1 h−1 in one-month-old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12-24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q10 factor increased from 2.25 to 3.43 with increasing size. Day-old yolk-sac larvae, late yolk-sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise.  相似文献   

10.
Pyruvate Carboxylase Activity in Primary Cultures of Astrocytes and Neurons   总被引:19,自引:17,他引:2  
Abstract: The activity of the pyruvate carboxylase was determined in brains of newborn and adult mice as well as primary cultures of astrocytes, of cerebral cortex neurons, and of cerebellar granule cells. The activity was found to be 0.25 ± 0.14, 1.24 ± 0.07, and 1.75 ± 0.13 nmol · min−1· mg−1 protein in, respectively, neonatal brain, adult brain, and astrocytes. Neither of the two types of neurons showed any detectable enzyme activity (i.e., < 0.05 nmol · min−1· mg−1). It is therefore concluded that pyruvate carboxylase is an astrocytic enzyme.  相似文献   

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