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991.
Cycloartenol derivatives are present in the non-photosynthetic parasitic plants Cuscuta europaea (dodder), Cuscuta epithymum and Orobanche lutea (broomrape). C.europaea and O.lutea are capable of biosynthesizing their own sterols. There is therefore no direct link, in a chlorophyll-containing phylum, between the cycloartenol pathway to sterols and photosynthesis. 相似文献
992.
In greening maize leaves δ-aminolevulinic acid (ALA) was not formed from succinyl-CoA and glycine as shown by the incorporation of [14C]-labeled 相似文献
993.
Zdzisław A. Wojciechowski 《Phytochemistry》1975,14(8):1749-1753
The synthesis of oleanolic acid 3β-d-glucuronoside from oleanolic acid and UDPGlcA has been demonstrated in cell-free preparations from C. officinalis seedlings. Moreover, the formation of more complex glycosides by successive additions of galactose and glucose to oleanolic acid glucuronoside was observed when cell-free preparations were incubated with UDPGal or UDPGlc. The consecutive steps of oleanolic acid glycosylation are localized in three different cellular compartments. The biosynthesis of the 3-glucuronoside takes place in the microsomes, the elongation of the sugar chain at C-3 of the aglycone proceeds in heavy membrane structures which are probably fragments of the Golgi complex while a cytosol enzyme(s) is involved in glucosylation of the C-17 carboxyl group of oleanolic acid. 相似文献
994.
Although all parts of the geranium plant (Pelargonium hortorum) are capable of synthesizing sterols and triterpenes and their esters in vitro from mevalonic acid-[2-14C], the aerial portions are more active than other tissues. All plant parts were shown to incorporate mevalonic acid-[2-14C] into isoprenoids for at least 3 days. The leaves and petioles had the greatest incorporation on a wet weight basis. Chopped preparations showed comparable incorporations of mevalonate whereby rootlets incorporated about one half as much as most parts; the flower petals incorporated five times the average amount. In leaves the principal sterol synthesized was sitosterol. Metabolic studies with isolated leaves indicated a fairly rapid conversion of free tetracyclic triterpenes to 4-desmethyl-sterols, while β-amyrin was synthesized at a different rate than α-amyrin. Esterified tetracyclic triterpenes exhibited only a slight amount of conversion to 4-desmethylsterols. 相似文献
995.
Alain Nicolas Jaques Bascoul André Crastes De Paulet Peter D.G. Dean 《Phytochemistry》1975,14(11):2407-2409
The incubation of [1-14C]-squalene-2(3)epoxide ([1-14C]-SO) with a cell-free extract of Alnus glutinosa gave only cycloartenol in 1% yield. 相似文献
996.
An enzyme was detected in petal extracts of Melandrium album which catalysed the transfer of the xylose moiety of UDP-xylose to the 7-hydroxyl group of isovitexin. Genetical analysis revealed that the presence of the dominant allele gx was necessary for enzymic activity. This activity was independent of the residual genetic background. Xylosyltransferase activity is also present in extracts of gGgx plants, in which the product of the enzyme is not detectable. Maximal activity was found between pH 7·0 and 7·5; MnCl2 inhibited this transfer. The enzyme had an ‘apparent Km' value of 1·0 mM for UDP-xylose and of O·04 mM for isovitexin. 相似文献
997.
The conversion of ent-kaur-16-enes to gibberellic acid in Gibberella fujikuroi is blocked by A-ring modifications. Thus ent-3β-hydroxykaur-16-en-19-yl succinate gives good conversion (46%) to the 7β-hydroxy derivative.* Under the same conditions the 3β-epimer gives 7β- or 6α-hydroxylation and the former occurs for the 3-oxo analogue. The succinoyloxy function acts as a less efficient block and ent-kaur-16-en-19-yl succinate is converted to 7β-hydroxy and 6β,7β-dihydroxy derivatives along with gibberellic acid. Hydrolysis of the succinate block of the metabolities provides the 7β, 19-diol and 6β,7β, 19-triol. Of this pair only the former was effectively metabolized to gibberellic acid in G. fujikuroi. 相似文献
998.
Biosynthesis of gibberellins A12, A15, A24, A36, and A37 by a cell-free system from Cucurbita maxima
GA12-aldehyde obtained from mevalonate via ent-kaurene, ent-kaurenol, ent-kaurenoic acid and ent-7α-hydroxykaurenoic acid in a cell-free system from immature seeds of Cucurbita maxima was converted to GA12 by the same system. When Mn2+ was omitted from the system GA12-aldehyde and GA12 were converted further to several products. Among these GA15, GA24, GA36 and GA37 were conclusively identified by GC-MS. With the exception of GA37 these GAs have not previously been found in higher plants. Another biosynthetic pathway led from ent-7α-hydroxykaurenoic acid to very polar products via what was tentatively identified as ent-6α, 7α-dihydroxykaurenoic acid. An unidentified component with an MS resembling that of a dihydroxykaurenolide was also obtained from incubations with mevalonate. 相似文献
999.
Occurrence of a 3′-phosphoadenosine 5′-Phosphosulphate synthesizing system In two Ochromonas species
The presence of an enzyme capable of incorporating 35SO42? into 3′-phosphoadenosine 5′-phosphosulphate has been demonstrated,in Ochromonas danica and O. malhamensis. This system probably includes the enzymes ATP:sulphate adenyltransferase. E.C. 2.7.7.4 and ATP:adenylsulphate 3′-phosphotransferase, E.C. 2.7.1.25. 相似文献
1000.
Ivan F. Bird Martin J. Cornelius Alfred J. Keys Charles P. Whittingham 《Phytochemistry》1974,13(1):59-64
Improved conditions for extraction and assay increased rates of sucrose synthesis from uridine diphosphate glucose (UDPglucose) plus fructose 6-phosphate (F.6.P) catalysed by leaf extracts 20-fold. Rates of 17.9, 25·0, 9·2 and 27·7 μmol/hr/g fr. wt respectively were obtained from pea shoots, spinach, wheat and bean leaves. Chloroplasts isolated from pea shoots, in which half the plastids were intact, contained less than 4% of the total UDPglucose-fructosephosphate glucosyltransferase, more than 30% of the ribulose diphosphate (RuDP) carboxylase, and more than 40% of the total chlorophyll of the leaf. Although some of the UDPglucose-fructose-phosphate glucosyltransferase was associated with particles smaller than chloroplasts at least 85% of the enzyme was not precipitated at 38 000 g. UDPglucose pyrophosphorylase, also thought to be essential for sucrose synthesis, was distributed between the cell fractions in a similar manner to UDPglucose-fructosephosphate glucosyltransferase. It is concluded that sucrose synthesis in pea shoots and spinach leaves occurs mainly, in the cytoplasm. 相似文献