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1.
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
8.
A model of the C
3 photosynthetic system is developed which describes the sensitivity of the steadystate rate of carbon dioxide assimilation to changes in the activity of several enzymes of the system. The model requires measurements of the steady-state rate of carbon dioxide assimilation, the concentrations of several intermediates in the photosynthetic system, and the concentration of the active site of ribulose 1,5-bisphosphate carboxyalse/oxygenase (Rubisco). It is shown that in sunflowers (Helianthus annuus L.) at photon flux densities that are largely saturating for the rate of photosynthesis, the steady-stete rate of carbon dioxide assimilation is most sensitive to Rubisco activity and, to a lesser degree, to the activities of the stromal fructose, 6-bisphosphatase and the enzymes catalysing sucrose synthesis. The activities of sedoheptulose 1,7-bisphosphatase, ribulose 5-phosphate kinase, ATP synthase and the ADP-glucose pyrophosphorylase are calculated to have a negligible effect on the flux under the high-light conditions. The utility of this analysis in developing simpler models of photosynthesis is also discussed.Abbreviations
c
i
intercellular CO2 concentration
-
C
infP
supJ
control coefficient for enzyme P with respect to flux J
- DHAP
dihydroxyacetonephosphate
- E4P
erythrose 4-phosphate
- F6P
fructose 6-phosphate
- FBP
fructose 1,6-bisphosphate
- FBPase
fructose 1,6-bisphosphatase
- G3P
glyceraldehyde 3-phosphate
- G1P
glucose 1-phosphate
- G6P
glucose 6-phosphate
- Pi
inorganic phosphate
- PCR
photosynthetic carbon reduction
- PGA
3-phosphoglyceric acid
- PPFD
photosynthetically active photon flux density
-
R
n
J
response coefficient for effector n with respect to flux J
- R5P
ribose 5-phosphate
- Rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase
- Ru5P
ribulose 5-phosphate
- RuBP
ribulose 1,5-bisphosphate
- S7P
sedoheptulose 7-phosphate
- SBP
sedoheptulose 1,7-bisphosphate
- SBPase
sedoheptulose 1,7-bisphosphatase
- SPS
sucrose-phosphate synthase
- Xu5P
xylulose 5-phosphate
-
n
P
elasticity coefficient for effector n with respect to the catalytic velocity of enzyme P
This research was funded by an Australian Research Council grant to I.E.W. and was undertaken during a visity by K.A.M. to the James Cook University of North Queensland. The expert help of Glenys Hanley and Mick Kelly is greatly appreciated. 相似文献
9.
Algorithms and software tools for ordering clone libraries: application to the mapping of the genome of Schizosaccharomyces pombe. 总被引:3,自引:1,他引:2 下载免费PDF全文
A complete set of software tools to aid the physical mapping of a genome has been developed and successfully applied to the genomic mapping of the fission yeast Schizosaccharomyces pombe. Two approaches were used for ordering single-copy hybridisation probes: one was based on the simulated annealing algorithm to order all probes, and another on inferring the minimum-spanning subset of the probes using a heuristic filtering procedure. Both algorithms produced almost identical maps, with minor differences in the order of repetitive probes and those having identical hybridisation patterns. A separate algorithm fitted the clones to the established probe order. Approaches for handling experimental noise and repetitive elements are discussed. In addition to these programs and the database management software, tools for visualizing and editing the data are described. The issues of combining the information from different libraries are addressed. Also, ways of handling multiple-copy probes and non-hybridisation data are discussed. 相似文献
10.