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191.
Acetyl coenzyme A (CoA) biosynthesis in spinach chloroplasts has been investigated by following the incorporation of bicarbonate and acetate into fatty acids under a variety of conditions. Both substrates were readily incorporated into fatty acids in a light-dependent manner by intact photosynthesising chloroplasts, but when the concentrations of these substrates were adjusted to those found in vivo, i.e. 200 M acetate, 10 M bicarbonate, then acetate was found to supply carbon atoms for fatty acids biosynthesis via acetyl CoA at forty times the rate of bicarbonate. It is proposed that extra-chloroplastic free acetate is the pricipal substrate for chloroplasts acetyl CoA biosynthesis in spinach.Abbreviations ACP
acyl carrierprotein
- CoASH
coenzyme A 相似文献
192.
The properties of transketolase from photosynthetic tissue 总被引:1,自引:0,他引:1
Transketolase (E.C. 2.2.1.1.) has been partially purified from wheat (Triticum aestivum, cv. Sappo) and spinach (Spinacia oleracea) leaves. The fully-active enzyme is a tetramer of relative molecular mass (Mr) of 150 kMr requiring thiamin pyrophosphate for maximal activity, and dissociating into a 74 kMr dimer in its absence or in dilute solution. The chloroplastic transketolase (over 75% of the cellular total) is magnesium-stimulated but the cytosolic form is magnesium-insensitive. Both chloroplastic and cytosolic transketolase showed similar broad specificities towards several ketose phosphate substrates including fructose 6-phosphate and sedoheptulose 7-phosphate. Wheat and spinach leaf transketolases are not light-activated and closely resemble the yeast enzyme in many of their properties.Abbreviations Mr
relative molecular mass
- TPP
thiamin pyrophosphate
- Tris
2-amino-2-(hydroxymethyl)-1,3-propandiol 相似文献
193.
George J. P. Murphy 《Planta》1980,149(5):417-426
Naphthalene-1-acetic acid (NAA) binding by membrane fractions derived from maize has been re-evaluated. Using a computer curve-fitting procedure only one major type of NAA binding, in terms of binding affinity, could be identified. Auxins, antiauxins and structurally related compounds have been tested for their competitive effect on NAA binding and the inhibitor constants for a number of these have been determined. Extracts from various plant species have been examined for their NAA binding ability, but all showed much less binding than maize leaf or coleoptile preparations. The possibility of the NAA binding by maize extracts being due to a true hormone receptor is discussed.Abbreviations BA
benzoic acid
- CPIB
p-chlorophenoxyisobutyric acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- DCB
2,4-dichlorobenzoic acid
- IAA
indolyl-3-acetic acid
- NAA
napthalene-1-acetic acid
- 2-NAA
napthalene-2-acetic acid
- NAOA
napthalene-2-oxyacetic acid
- PA
phenylacetic acid
- PU
phenylurea
- 2,4,5-T
2,4,5-trichlorophenoxyacetic acid
- TIBA
2,3,5-triiodobenzoic acid 相似文献
194.
In Vivo Pathway of Oleate and Linoleate Desaturation in Developing Cotyledons of Cucumis sativus L. Seedlings 总被引:6,自引:5,他引:1 下载免费PDF全文
Exogenous [1-14C]oleic acid and [1-14C]linoleic acid were taken up and esterified to complex lipids by greening cucumber (Cucumis sativus L.) cotyledons. Both 14C-labeled fatty acids were initially esterified to phosphatidylcholine prior to eventual accumulation in triacylglycerols and galactolipids. Kinetic data suggest that esterification occurs prior to desaturation and that phosphatidylcholine is the initial site of both [14C]-oleate and [1-14C]linoleate esterification and of [1-14C]oleate desaturation to [1-14C]linoleate. [1-14C]Linoleic acid was esterified more rapidly than [14C]oleic acid and its desaturation product, [1-14C]α-linolenate, occurred mainly on monogalactosyl diacylglycerol, although some was also observed on the other major acyl lipids, including phosphatidylcholine. 相似文献
195.
Joe Murphy Roger Rowlett Susan B. Smith James Hoeferlin 《Archives of biochemistry and biophysics》1980,202(2):405-413
The KI values for inhibition of thermolysin activity by N-β-phenylpropionyl-aliphatic amino acids (Gly, Ala, Val, Leu, Ile) are correlated by π, the hydrophobic substituent parameter for the amino acid side chain (log KI = ?0.73π ?1.80, correlation coefficient = 0.990). By contrast, the KI values for the corresponding benzyloxycarbonyl amino acids are poorly correlated by π, but show a good correlation with the steric parameter Es(log KI = 0.880Es ? 3.086, correlation coefficient = 0.985). Binding of β-phenylpropionyl-l-alanine is associated with an acidic residue of pK 7.3 and a basic residue of pK 8.0 in the E · I complex, and appears to raise the pK of Glu-143 by 2 units. Binding of benzyloxycarbonyl-Ala and -Phe is associated with an acidic residue of pK 8.0 and two basic residues, both with pK 8.3. Three similar pK values are observed with benzyloxycarbonyl-Phe. These results are interpreted in terms of different modes of binding of β-phenylpropionyl and benzyloxycarbonyl inhibitors. 相似文献
196.
Identification of rat brain polysomes synthesizing the brain specific enolase (14.3.2 protein), S100 protein and alpha and beta tubulin subunits 总被引:1,自引:0,他引:1
A Marks M M Portier Y Zeitoun L Legault-Demare J Thibault N Lamande C Jeantet F Gros 《Biochimie》1980,62(7):463-471
Polysomes prepared from frozen rat brain powder were fractionated by centrifugation in a sucrose gradient. Individual fractions were used to program a reticulocyte lysate in a run-off reaction. The products of cell-free synthesis were assayed for the brain-specific enolase (14.3.2 protein) and S100 protein by immunoprecipitation with specific antisera and for tubulin by two-dimensional electrophoresis in polyacrylamide slab gels. The relative synthesis of these proteins by unfractionated free brain polysomes were 0.1 per cent, 0.05 per cent and 0.7 per cent respectively. After centrifugation in a sucrose gradient polysomes synthesizing S100 protein were separated from those synthesizing the other two markers. There was a threefold enrichment in the specific messenger RNA activity for each of the three proteins studied in their respective peak fractions of polysomes. 相似文献
197.
198.
Leaf slices from spinach exhibited considerable variation in their incorporation of [14C]bicarbonate and [1-14C]acetate into fatty acids. Reductive ozonolysis studies indicated that all the 14C-labeled fatty acids were synthesized de novo; no in vivo evidence was found for the previously proposed elongation of hexadecatrienoate to α-linolenate. 相似文献
199.
A strain of cultured cells of Rosa damascena Mill. which showed unusual resistance to damage by short wave (254 nanometers) ultraviolet radiation was isolated. The resistant cells were 2.2 to 2.8 times larger and had about twice the amount of DNA and more chromosomes than the parental, sensitive cells. The resistant cells also produced larger quantities of polyphenolic compounds, principally flavonoids, during the later phases of culture growth. At 10 days, resistant cells had 4 times more nonflavonoid polyphenolics and 14 times more flavonoids than parental cells. The resistance, which was also observed only in the later phases of culture growth, was best correlated with the production of polyphenolics, which apparently shielded ultraviolet-sensitive target molecules from damage. 相似文献
200.
Summary This paper discusses optimal harvesting policies for age-structured populations harvested with effort independent of age. 相似文献