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1.
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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3.
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
4.
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
5.
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
6.
Rowan Jenkins 《The Botanical review》1993,59(2):81-111
A review of methods used in the taxonomy of the Fagaceae is presented, with a critical focus made on the nomenclature of extant and fossil taxa, notablyNothofagus. The most recent classifications of the family and the problems of character weighting are considered, and an argument is made to reduce the subfamilies to tribes. The origin of the cupule is then discussed. Interpretations of the cupule as a series of reduced dichasial axes are criticized for their essentialistic approach, lack of evolutionary evidence and failure of application to the family as a whole. With the postulating of an ancestral form, the origin of the cupule involving a combination of characters from an outer tripartite perianth whorl and the pericarp is proposed. The theory provides for the evolution of the thin-walled dry pericarp and all the cupule forms found in the family today. 相似文献
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8.
Steven A. Akman Fumiyo Kusu Kiyoko Takamura Rowan Chlebowski Jerome Block 《Analytical biochemistry》1984,141(2):488-493
A differential pulse polarographic assay for plasma vitamin K3 (menadione) has been developed. Details of the assay are (i) lipid-soluble material is extracted from plasma into ether by the method of Bjornsson et al. [(1978) Thromb. Haemostas.2, 466–473]; (ii) ether is evaporated under nitrogen and the residue is dissolved in the supporting electrolyte, methanol: 0.2 m borate buffer (9:1), pH 6.8; (iii) current height is measured at ?0.32 V vs SCE on the differential pulse polarogram. The lower sensitivity limit of this technique after addition of standard vitamin K3 to plasma is 0.3 μm; the calibration curve is linear from 0.6 through 10 μm. Two patients treated with a single dose of menadiol sodium diphosphate, 20 mg/M2 i.m., achieved measurable plasma vitamin K3 levels at 0.5 to 1.0 h ranging between 0.5 (0.08 μg/ml) and 2 μm (0.3 μg/ml). 相似文献
9.
Expression of rat procathepsin B in yeast led to the secretion of both the latent and mature forms of the enzyme. Culture in the presence of a cysteine proteinase inhibitor prevented this processing. We have expressed and purified a mutant form of rat procathepsin B whose active-site cysteine residue has been changed to a serine, and which also lacks the glycosylation site in the mature region of the protein. This non-active mutant protein was secreted essentially in an unprocessed form. The purified protein has been incubated with a variety of proteinases, and results indicate that cathepsins D and L, as well as mature cathepsin B itself, can produce a processed (single-chain) form of cathepsin B from this precursor. Amino-terminal sequencing of these processed forms has revealed that they are all elongated by a few residues with respect to the mature form found in vivo. The action of a combination of cathepsin B with dipeptidylpeptidase I produced a single-chain form of cathepsin B with the correct amino terminus. This work has also shown that the processing of procathepsin B to a single-chain form can be an autocatalytic process, in at least an intermolecular manner. 相似文献
10.
Plant growth inhibitors of the podolactone-type have been detected by bioassay in ten further species of Podocarpus. The most active extracts in P. elatus were from root tips, root cortex and very young leaves. Fifty-seven other conifers were examined for this type of activity. It is present in Cephalotaxus harringtonia where it is probably due to the presence of harringtonolide, which, like momilactone B from rice husks, shows podolactone-type inhibition of the growth of etiolated dwarf pea hooks. 相似文献