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1.
J. Ruiz-Herrera J. P. Martinez M. Casanova M. L. Gil R. Sentandreu 《Archives of microbiology》1987,149(2):156-162
Cells from the slime variant of Neurospora crassa were broken in isotonic conditions by use of triethanolamine buffer plus EDTA. After removal of large membranous structures by low-speed centrifugation, chitosomes and secretory vesicles were separated by means of gel filtration, precipitation of membranous contaminants with Concanavalin A, and centrifugation in sucrose or glycerol gradients. Polypeptidic composition of fractions enriched in secretory vesicles or chitosomes was found to be distinct. By these criteria we concluded that chitosomes and secretory vesicles represent different populations of microvesicles. Both microvesicular populations appeared free of endoplasmic reticulum and vacuolar contaminants as demonstrated by determination of appropriate enzymatic markers.Abbreviations ER
Endoplasmic reticulum
- UDP-GlcNAc
uridine-5-diphosphate N-acetyl glucosamine
- GlcNAc
N-acetyl glucosamine
- SDS
sodium dodecyl sulfate
- PMSF
phenyl methyl sulfonyl fluoride
- EDTA
ethylene diamino tetraacetic acid
Investigador Nacional de Mexico. On leave from the Centro de Investigacion y Estudios Avanzados (IPN), and the Universidad de Guanajuato, Gto., Mexico 相似文献
2.
The β-fructofuranosidase from Kluyveromyces fragilis was purified to one band on electrophoresis by 3 different methods. Two of the preparations were found to be impure by isoelectric focusing. This demonstrates the need for more than one criteria of homogeneity when purifying this enzyme. The enzyme was found to be a glycoprotein, stable at 50°C, with a pH optimum of 4.5. The cations Hg2+, Ag+, Cu2+ and Cd2+ exhibited a marked inhibition of the enzyme. Competitive inhibition was observed with the fructose analog 2,5-anhydro-D-mannitol suggesting that the enzyme is inhibited by the furanose form of fructose. 相似文献
3.
The identification of genes associated with ecologically important traits provides information on the potential genetic mechanisms underlying the responses of an organism to its natural environment. In this study, we investigated the genetic basis of host plant resistance to the gall-inducing aphid, Pemphigus betae, in a natural population of 154 narrowleaf cottonwoods (Populus angustifolia). We surveyed genetic variation in two genes putatively involved in sink-source relations and a phenology gene that co-located in a previously identified quantitative trait locus for resistance to galling. Using a candidate gene approach, three major findings emerged. First, natural variation in tree resistance to galling was repeatable. Sampling of the same tree genotypes 20 years after the initial survey in 1986 show that 80% of the variation in resistance was due to genetic differences among individuals. Second, we identified significant associations at the single nucleotide polymorphism and haplotype levels between the plant neutral invertase gene NIN1 and tree resistance. Invertases are a class of sucrose hydrolyzing enzymes and play an important role in plant responses to biotic stress, including the establishment of nutrient sinks. These associations with NIN1 were driven by a single nucleotide polymorphism (NIN1_664) located in the second intron of the gene and in an orthologous sequence to two known regulatory elements. Third, haplotypes from an inhibitor of invertase (C/VIF1) were significantly associated with tree resistance. The identification of genetic variation in these two genes provides a starting point to understand the possible genetic mechanisms that contribute to tree resistance to gall formation. We also build on previous work demonstrating that genetic differences in sink-source relationships of the host influence the ability of P. betae to manipulate the flow of nutrients and induce a nutrient sink. 相似文献
4.
J.E. Sayago M.A. Vattuone A.R. Sampietro M.I. Isla 《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):123-130
An acid invertase from the fern Pteris deflexa Link was purified and the effect of reaction products on enzyme activity was studied. Fructose and glucose were competitive and non-competitive inhibitors of the enzyme, respectively. Since proteins suppressed glucose and fructose inhibition of the enzyme, an invertase modulation by reaction products is unlikely; nevertheless, an invertase proteinaceous inhibitor previously reported could have a role in this respect. The purified enzyme was an heterodimer M r 90,000 Daltons composed of subunits of 66,000 and 30,000 Daltons. The enzyme had β -fructofuranosidase activity and hydrolyzed mainly sucrose but also raffinose and stachyose, with K m of 3.22, 10.80 and 38.50 mM, respectively. Invertase activity with an optimum pH at 5.0 was present in almost every leaf fern tissue. Pinnas (sporophyll leaflets) had the higher enzyme levels. Invertase histochemical and immunochemical localization studies showed the enzyme mainly in phloem cells. Epidermis, collenchyma and parenchyma cells also showed invertase protein. 相似文献
5.
抗坏血酸对酵母蔗糖酶的激活动力学研究 总被引:4,自引:0,他引:4
采用甲苯自溶法从鲜酵母中提取了蔗糖酶,并用乙醇分级及DEAE-纤维素柱层析进行了纯化,用PAG凝胶电泳作了纯度鉴定,在pH5.0,30℃条件下进行了酶反应,用双倒数作图法测出其Km=2.1×10-2mol/L,Vmax=0.26(每分钟的光密度值).在此系统中,加入不同浓度的抗坏血酸(Vit.C),发现其具有激活作用并存在量效关系.双倒数作图显示:酶的表观Vmax(Vp)随抗坏血酸浓度的增加而增大,但其表观Km(Kp)不变(Kp=Km).经实验结果分析,推论出抗坏血酸激活作用的酶促反应方程式,并推导出反应速度公式 相似文献
6.
In order to better understand the various pathways of sucrose and starch catabolism in the anther of lily (Lilium hybrida var. “Enchantment”), invertase (EC 3.2.1.26) and amylase (EC 3.2.1.1, EC 3.2.1.2) activities were measured separately in
different fractions (anther wall, locular fluid and microspore/pollen) and correlated with the sugar content during anther
development. Our findings showed significant differences among the fractions analyzed, suggesting that the regulation of sucrose
and starch catabolism could follow distinct pathways in each fraction. Glucose and fructose amounts progressively decreased
from anther wall to fluid and from fluid to microspore/pollen. Thus, the developing pollen could act as a sink for the carbohydrates
that reach the anther. In this sense, cell wall-bound invertases seem to play a major role in soluble sugar partitioning in
the different fractions of the anther. Sucrose concentration was found to be substantially higher in the locular fluid than
in the other fractions, indicating a probable site for storage. On the other hand, the anther wall tissues could have a buffering
function, storing nutrient surplus in starch grains and thus regulating the availability of soluble sugars in the whole anther.
All these results proved the advantages of the experimental model proposed here, as well as its usefulness to investigate
sugar metabolism in Lilium anthers. 相似文献
7.
The effect of addition of indole acetic acid (3 M) andNaCl (75 mM) on growth and enzymes of carbohydrate metabolism inchickpea seedlings was compared. In comparison with control seedlings, theseedlings growing in the presence of indole acetic acid (IAA) had reducedamylase activity in cotyledons and enhanced sucrose synthase (SS) and sucrosephosphate synthase (SPS) activities in cotyledons and shoots at all days ofseedling growth. Compared with control seedlings, sucrose content was higher incotyledons, shoots and roots and reducing sugar content was lower in shoots ofIAA treated seedlings. A low invertase (acid and alkaline) activity in shoots ofIAA treated seedlings could lead to reduced sink strength and hence decreasedgrowth of seedlings. Effects of NaCl stress on growth and activities of amylase,SS and SPS in cotyledons and invertase, SS and SPS in shoots were similar tothose observed with addition of IAA. 相似文献
8.
The present study investigates the efficiency of Aspergillus niger to produce invertase, an industrially important enzyme by using powdered stem of Cympopogan caecius (Lemon grass) as sole substrate and sole carbon source for the microorganism. The molecular weight of invertase was estimated
to be 66–70 kDa by sodium do decyl sulphate poly acrylamide gel electrophoresis (SDS PAGE). The production of the enzyme was
studied at different pH scales ranging from pH 4.0 to 7.0 at a constant temperature of 30°C and 2% substrate concentration.
The maximum production of invertase (specific activity −0.0516 μk/mg protein) was obtained at pH 5.5 at 30°C temperature,
and incubation for 48 h. The activity was found to be stable at pH 5.5 for 30 min. The enzyme was found to be stable in the
temperature range of 20–55°C. The effect of divalent metal ions Cu2+, Fe2+, Co2+ on the activity of the enzyme invertase showed that these ions affected the activity by a certain factor. The study can be
further industrially exploited in a country-like India where lemon grass is found in plenty and can be used as substrate for
enzyme production. Moreover, the preparation of the substrate is also a simple process. 相似文献
9.
Solute accumulation and decreased photosynthesis in leaves of potato plants expressing yeast-derived invertase either in the apoplast, vacuole or cytosol 总被引:11,自引:0,他引:11
Dirk Büssis Dieter Heineke Uwe Sonnewald Lothar Willmitzer Klaus Raschke Hans-Walter Heldt 《Planta》1997,202(1):126-136
Potato (Solanum tuberosum cv. Désirée) plants expressing yeast invertase directed either to the apoplast, vacuole or cytosol were biochemically and
physiologically characterised. All lines of transgenic plants showed similarities to plants growing under water stress. Transformants
were retarded in growth, and accumulated hexoses and amino acids, especially proline, to levels up to 40-fold higher than
those of the wild types. In all transformants rates of CO2 assimilation and leaf conductance were reduced. From the unchanged intercellular partial pressure of CO2 and apoplastic cis-abscisic acid (ABA) content of transformed leaves it was concluded that the reduced rate of CO2 assimilation was not caused by a limitation in the availability of CO2 for␣the ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco). In the transformants the amount of Rubisco protein was
not reduced, but both activation state and carboxylation efficiency of photosynthesis were lowered. In vacuolar and cytosolic
transformants this inhibition of Rubisco might be caused by a changed ratio of organic bound and inorganic phosphate, as indicated
by a doubling of phosphorylated intermediates. But in apoplastic transformants the pattern of phosphorylated intermediates
resembled that of leaves of water-stressed potato plants, although the cause of inhibition of photosynthesis was not identical.
Whereas in water-stressed plants increased contents of the phytohormone ABA are supposed to mediate the adaptation to water
stress, no contribution of ABA to reduction of photosynthesis could be detected in invertase transformants.
Received: 29 May 1996 / Accepted: 30 December 1996 相似文献
10.