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131.
132.
133.
Fructan biosynthesis in excised leaves of Lolium temulentum L. 总被引:10,自引:10,他引:0
134.
We isolated hybridomas that produced monoclonal antibodies specific for the UDP-galactose: sn -glycerol-3-phosphate α-D-galactosyltransferase (IFP synthase, EC 2.4.1.96), an enzyme involved in the volume regulation of Poterioochromonas malhamensis Peterfi. Western blotting of native gradient gels with the most reactive antibody S 162 revealed several immunoreactive proteins in crude homogenates suggesting the occurrence of multiple molecular mass species of the galactosyltransferase. The amount of the presumed enzyme monomer (64 kDa under native conditions) was strongly increased by a pH shift of crude homogenates from pH 8 to 6. During activation of the galactosyltransferase in the cell homogenate and also by shrinking the cells, the presumed enzyme monomer appeared to be proteolytically degraded generating stepwise products of 52 and 40 kDa. We assume that the proteolytically processed enzyme becomes highly active, but is very susceptible to further proteolytic degradation. 相似文献
135.
Carnitine-acyltransferase activity assayed with acetyl-CoA, octanoyl-CoA, or palmitoyl-CoA is associated with the mitochondrial but not with the peroxisomes of mung-bean hypocotyls. Using mitochondria as an enzyme source, a half-maximal reaction rate is obtained with a palmitoyl-CoA concentration approximately twice that required with acetyl-CoA. In the presence of a saturating acetyl-CoA concentration the carnitine-acyltransferase activity is not enhanced by palmitoyl-CoA as additional substrate. However, palmitoylcarnitine is formed in addition to acetylcarnitine, and the formation of acetylcarnitine is competitively inhibited by palmitoyl-CoA. It is concluded that the mitochondria of mung-bean hypocotyls possess a carnitine acyltransferase of broad substrate specificity with respect to the chainlength of the acyl-CoA and that the demonstration of a carnitine-palmitoyltransferase activity in plant mitochondria does not indicate the presence of a specific carnitine long-chain acyltransferase. 相似文献
136.
137.
Päivi Heikkilä Arvi I. Kahri Christian Ehnholm Petri T. Kovanen 《In vitro cellular & developmental biology. Plant》1988,24(9):936-942
Summary To define the role of endogenously synthesized cholesterol in the differentiation of adrenocortical cells in primary culture,
fetal rat adrenal cells were cultured in the presence of exogenous cholesterol (serum-supplemented medium) or in the absence
of it (serum-free medium or lipoprotein-free medium). Ultrastructurally the cells had features of glomerulosa cells: mitochondria
were oval or rod shaped with lamellar inner membranes. The amount of smooth endoplasmic reticulum was small, and lipid droplets
were few. When the cells were cultured in serum-free medium some intracytoplasmic vacuoles were seen. The undifferentiated
zona glomerulosa-like cells secreted low amounts of corticosterone and 18-OH-deoxycorticosterone (18-OH-DOC) in all three
media (serum-supplemented medium, serum-free medium, and lipoprotein-free medium). Stimulation of the adrenocortical cells
with ACTH induced the ultrastructural features of differentiated zona fasciculata-like cells. Mitochondrial inner membranes
were well developed in lipoprotein-free medium, but not in serum-free medium. The amount of intracellular lipids was increased
in both media devoid of cholesterol. In the ACTH stimulated cultures the presence of exogenous cholesterol resulted in increased
secretions of corticosterone and 18-OH-DOC. In the absence of an exogenous source of cholesterol, the amounts of steroids
secreted were only half of that secreted in the presence of serum-supplemented medium. Endogenously synthesized cholesterol
is sufficient for the morphologic differentiation of fetal rat adrenocortical cells under ACTH stimulation. However, without
exogenously provided cholesterol, the steroid production accounts only for half of the maximal output achieved using serum-supplemented
medium.
This work was supported by Finnish Culture Foundation. 相似文献
138.
Maria F. S. Barbosa Maria B. de Medeiros Ismael M. de Mancilha Henry Schneider Hung Lee Ph.D. 《Journal of industrial microbiology & biotechnology》1988,3(4):241-251
Summary The ability to convertd-xylose to xylitol was screened in 44 yeasts from five genera. All but two of the strains produced some xylitol with varying rates and yields. The best xylitol producers were localized largely in the speciesCandida guilliermondii andC. tropicalis. Factors affecting xylitol production by a selectedC. guilliermondii strain, FTI-20037, were investigated. The results showed that xylitol yield by this strain was affected by the nitrogen source. Yield was highest at 30–35°C, and could be increased with decreasing aeration rate. Using high cell density and a defined medium under aerobic conditions, xylitol yield byC. guilliermondii FTI-20037 from 104 g/ld-xylose was found to be 77.2 g/l. This represented a yield of 81% of the theoretical value, which was computed to be 0.9 mol xylitol per mold-xylose.Issued as NRCC publication No. 28798. 相似文献
139.
C Sartori S Stefanini A Cimini A Di Giulio M P Cerù 《Biology of the cell / under the auspices of the European Cell Biology Organization》1992,74(3):315-324
The fatty-acyl-CoA beta-oxidation (FAO) and catalase activities, as well as membrane fluidity of liver peroxisomes of newborns from normal and clofibrate-treated rats were studied during the recovery period, ie, throughout the first week of postnatal life. In the test animals the enzyme activities, which are significantly higher than controls at birth return to normal levels showing a somewhat different time course with FAO rapidly decreasing to control values within three days but with catalase still higher than controls at day 6. The half-life and degradation rate (Kd) of FAO are identical to those calculated by us for the whole organelles and to those reported by others for total catalase in normal or clofibrate-treated adult animals in the presence of catalase inhibitors. Soluble catalase shows turnover values which are similar though not identical to those of FAO, while total catalase has a very long half-life and a low Kd. Peroxisomal membrane fluidity, as determined by fluorescence anisotropy of 1-anilinonaphthalene-8-sulfonate (ANS) bound to purified peroxisomal fractions is higher in tests than in controls, recovering normal values within 6 days. Our results demonstrate that liver peroxisomes of rats prenatally exposed to clofibrate return to control conditions within about 1 week. The turnover parameters of enzymes and the membrane fluidity values are discussed in terms of disposal mechanism(s) for the excess of induced peroxisomes. 相似文献