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排序方式: 共有989条查询结果,搜索用时 15 毫秒
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Willoughby de Broke Rudyard Kipling Hugh Elliot E. Ray Lankester Leonard Hill Laurence R. Philipps Wm. Arbuthnot Lane James Crichton-Browne H. Bryan Donkin Francis Lloyd R. A. Lyster John MacAlister F. W. Mott William Osler C. W. Saleeby J. H. Sequeira Humphry Rolleston Hugh Wansey Bayly 《BMJ (Clinical research ed.)》1919,2(3074):725
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The pineapple plant (Ananas comosus) was shown to contain at least four distinct cysteine proteinases, which were purified by a procedure involving active-site-directed affinity chromatography. The major proteinase present in extracts of plant stem was stem bromelain, whilst fruit bromelain was the major proteinase in the fruit. Two additional cysteine proteinases were detected only in the stem: these were ananain and a previously undescribed enzyme that we have called comosain. Stem bromelain, fruit bromelain and ananain were shown to be immunologically distinct. Enzymic characterization revealed differences in both substrate-specificities and inhibition profiles. A study of the cysteine proteinase derived from the related bromeliad Bromelia pinguin (pinguinain) indicated that in many respects it was similar to fruit bromelain, although it was found to be immunologically distinct. 相似文献
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The short-term, in-vivo response to elevated CO2 of ribulose-1,5-bisphosphate carboxylase (RuBPCase, EC 4.1.1.39) activity, and the pool sizes of ribulose 1,5-bisphosphate, 3-phosphoglyceric acid, triose phosphates, fructose 1,6-bisphosphate, glucose 6-phosphate and fructose 6-phosphate in bean were studied. Increasing CO2 from an ambient partial pressure of 360–1600 bar induced a substantial deactivation of RuBPCase at both saturating and subsaturating photon flux densities. Activation of RuBPCase declined for 30 min following the CO2 increase. However, the rate of photosynthesis re-equilibrated within 6 min of the switch to high CO2, indicating that RuBPCase activity did not limit photosynthesis at high CO2. Following a return to low CO2, RuBPCase activation increased to control levels within 10 min. The photosynthetic rate fell immediately after the return to low CO2, and then increased in parallel with the increase in RuBPCase activation to the initial rate observed prior to the CO2 increase. This indicated that RuBPCase activity limited photosynthesis while RuBPCase activation increased. Metabolite pools were temporarily affected during the first 10 min after either a CO2 increase or decrease. However, they returned to their original level as the change in the activation state of RuBPCase neared completion. This result indicates that one role for changes in the activation state of RuBPCase is to regulate the pool sizes of photosynthetic intermediates.Abbreviations and symbols
A
net CO2 assimilation rate
- Ca
ambient CO2 partial pressure
- Ci
intercellular CO2 partial pressure
- CABP
2-carboxyarabinitol 1,5-bisphosphate
- kcat
catalytic turnover rate per RuBPCase molecule
- PFD
photon flux density (400 to 700 nm on an area basis)
- PGA
3-phosphoglyceric acid
- Pi
orthophosphate
- RuBP
ribulose 1,5-bisphosphate
- RuBPCase
ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) 相似文献
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Ananain: a novel cysteine proteinase found in pineapple stem 总被引:3,自引:0,他引:3
A previously unknown cysteine proteinase, named ananain, has been isolated from crude commercial pineapple stem bromelain. The purification procedure involved affinity chromatography on Sepharose-Gly-Phe-glycinaldehyde semicarbazone, and cation-exchange chromatography. The relative molecular mass of ananain was very similar to that of bromelain (25,000 and 26,000, respectively), but ananain differed greatly in specificity for hydrolysis of peptide and protein substrates. The new enzyme behaved as a typical cysteine proteinase in showing strong inhibition by chicken cystatin, whereas bromelain was scarcely affected. Ananain was also shown to be immunologically distinct from bromelain. The significance of the discovery of ananain for the interpretation of previous work on "bromelain" is pointed out. 相似文献
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Ronald J. Hill Margaret R. Mott Fujiko Watt Theodora Fifis P. Anne Underwood 《Chromosoma》1986,94(6):441-448
An antigen making a major contribution to the immune response to Drosophila melanogaster chromatin resides primarily on a nonhistone charge-class family of proteins of Mr 74,000. Immunofluorescence detects this antigen at interbands, puffs and diffuse bands of D. melanogaster salivary chromosomes isolated without exposure to acid fixatives, and on nucleoplasmic ribonucleoprotein droplets. In the electron microscope, gold labelling reveals the binding of monoclonal antibodies specific for the antigen at chromosomal loci generally bearing putative ribonucleoprotein (RNP) particles. However, the locus 3C 11–12 is remarkable in that it bears putative RNP particles but is virtually unlabelled, suggesting protein specificity at different active loci. 相似文献
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Effects of pH on Activity and Activation of Ribulose 1,5-Bisphosphate Carboxylase at Air Level CO(2) 总被引:9,自引:8,他引:1 下载免费PDF全文
The effects of pH on catalysis and activation characteristics of spinach ribulose 1,5-bisphosphate (RuBP) carboxylase were examined at air level of CO2. Catalysis at limiting CO2 was independent of pH over the range of pH 8.2 to 8.8 However, the kinetics of activation and the apparent equilibrium between the activated and inactivated forms of the enzyme were strongly dependent upon the pH and the presence or absence of the substrate RuBP. When incubated at air level of CO2 at pH 8.2 in the absence of RuBP, the enzyme activation state was approximately 75% of that achieved with saturating CO2 at that pH. The extent of activation increased with pH reaching 100% at pH values of 8.6 or higher. Adding RuBP to the activation medium after equilibrium activation state had been established decreased the apparent equilibrium activation level at pH values below 8.6. This effect was reversed at pH values above 8.6. Activation of inactive enzyme by CO2 and Mg2+ was inhibited dramatically at pH values below 8.6 and less so at pH values above 8.6. Studies showed that binding of RuBP to the inactive form of the enzyme was pH dependent with tighter binding occurring at lower pH values. It is suggested that the tight binding of RuBP to the inactive enzyme tends to decrease the equilibrium concentration of the activated form at pH values less than 8.6. These studies indicate that stromal pH could have a strong effect on the activation state of this enzyme in vivo, and possible feedback interactions which might adjust the apparent Vmax to match the rate of RuBP regeneration are discussed. 相似文献
10.
Activity of aminoacyl-transfer-ribonucleic acid synthetases in tobacco-leaf tissue in relation to senescence and to the action of 6-furfurylaminopurine 总被引:15,自引:7,他引:8 下载免费PDF全文
1. Streptomyces griseus was grown in a medium containing l-[Me-(14)C]methionine, and the labelled products from an ethanolic extract of the cells were examined. 2. Acid hydrolysis of one of the products gave a compound identified as 3-O-[Me-(14)C]-methylmannose by a series of degradative reactions. 3. Reduction of the radioactive compound gave 3-O-methyl-d-mannitol, indistinguishable from a synthetic sample. 相似文献