Showing papers on "Lanosterol published in 1968"
TL;DR: The mechanism of cycloartenol biosynthesis in leaves of Solanum tuberosum was investigated with the use of [2-(14)C,(4R)-4-(3)H(1)]mevalonic acid, demonstrating that the hydrogen atom at C-24 is retained during alkylation of the cycleartenol side chain.
Abstract: 1. The mechanism of cycloartenol biosynthesis in leaves of Solanum tuberosum was investigated with the use of [2-14C,(4R)-4-3H1]mevalonic acid. 2. The 3H/14C atomic ratio in cycloartenol was 6:6, the same as that in squalene; this eliminates lanosterol as a possible biosynthetic precursor of cycloartenol, and indicates that a hydrogen migration from C-9 to C-8 occurs. 3. Chemical isomerization of the cycloartenol to lanosterol (3H/14C ratio 5:6) and parkeol (3H/14C ratio 6:6) confirms the hydrogen migration from C-9 to C-8. 4. Possible mechanisms for the biosynthesis of cycloartenol and parkeol are discussed. 5. The 3H/14C ratio for 24-methylenecycloartanol was 6:6, demonstrating that the hydrogen atom at C-24 is retained during alkylation of the cycloartenol side chain.
60 citations
TL;DR: The results are in agreement with the predicted 1,2-H-migration3 during alkylation of the Δ24-bond and the position of the label in 24-ketocholesterol was shown to be C-25 by reduction to the labeled 24-hydroxy derivative followed by dehydration to desmosterol with loss of label.
40 citations
37 citations
TL;DR: Homogenates of human ovaries obtained from fetuses at 20 and 22 weeks of gestational age were incubated with sodium acetate-l-14C and small, but definite quantities of radioactive pregnenolone and progesterone were identified.
Abstract: Homogenates of human ovaries obtained from fetuses at 20 and 22 weeks of gestational age were incubated with sodium acetate-l-14C. The extracts were analyzed for sterols and steroids by the reverse isotope dilution technique. Purification and identification of the radioactive metabolites were achieved by paper and thin-layer chromatography, derivative formation and crystallization to constant specific activity. Evidence has been obtained for the formation of lanosterol and cholesterol. Small, but definite quantities of radioactive pregnenolone and progesterone were identified. No evidence was found for the formation of dehydroepiandrosterone, androstenedione, testosterone and estrogens.
35 citations
24 citations
TL;DR: It is shown that, in the biosynthesis of ergosterol from [26,27-(14)C(2),23-(3)H(2)]lanosterol by the whole cells of Saccharomyces cerevisiae, one of the original C-23 hydrogen atoms is lost and the other is retained at C- 23 of ergostol.
Abstract: Methods for the chemical synthesis of [23− 3 H 2 ]lanosterol, [23,25− 3 H 3 ]24-methyldihydrolanosterol and [24,28− 3 H 2 ]24-methyldihydrolanosterol are described. It is shown that, in the biosynthesis of ergosterol from [26,27− 14 C 2 ,23− 3 H 2 ]lanosterol by the whole cells of Saccharomyces cerevisiae , one of the original C-23 hydrogen atoms is lost and the other is retained at C-23 of ergosterol. It is also shown that 24-methyldihydrolanosterol is converted into ergosterol in good yield and without prior conversion into a 24-methylene derivative. On the basis of these results possible pathways for the formation of the ergosterol side chain from a 24-methylene side chain are discussed.
16 citations
TL;DR: It is suggested that sidechain methylation by S -adenosylmethionine may accompany or precede complete demethylation of lanosterol, which is similar to values obtained with mammalian microsomes.
16 citations
TL;DR: In this article, Lanosterol-14C was administered to the leaves of two Euphorbia peplus plants and radioactive sterol was isolated by extraction, saponification and chromatography.
14 citations
TL;DR: The results of this study do not support a primary causal relationship between the inhibition by DHA of glucose 6-phosphate dehydrogenase activity and of sterol synthesis.
Abstract: The addition of dehydroepiandrosterone (DHA) 3 × 10−5 to 3 × 10−4m to minced guinea pig mammary gland incubated with acetate-l-14C resulted in a strong inhibition of the labeling of squalene, lanosterol and cholesterol, and to a lesser extent of the glycerides. DHA strongly inhibited the activity of glucose 6-phosphate dehydrogenase (d-glucose 6-phosphate: nicotinamide adenine dinucleotide phosphate oxidoreductase, EC 1.1.1.49) of this tissue. Although 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: N ADP oxidoreductase decarboxylating, EC 1.1.1.44) was not inhibited by DHA, the addition of 6-phosphogluconate did not reverse the inhibition of cholesterol synthesis. However, the addition of 6-phosphogluconate reversed the inhibition by DHA of glyceride synthesis. The results of this study do not support a primary causal relationship between the inhibition by DHA of glucose 6-phosphate dehydrogenase activity and of sterol synthesis. (Endocrinology 83: 1311, 1968)
14 citations
Journal Article•
13 citations
TL;DR: The results indicate the presence in rat intestine of enzyme systems involved in the saturation of the Δ24-bond in lanosterol and its metabolites, the conversion of 7-dehydrocholesterol into cholesterol, and those inhibited by SKF 525-A, which means the pathway of intestinal cholesterol synthesis is similar to that of the liver.
Abstract: SummaryAY-9944, SKF 525-A, triparanol, and 22,25-diazacholestanol, agents known to inhibit hepatic cholesterol synthesis, suppressed the incorporation of acetate-[2-14C] and mevalonate-[3H] into cholesterol by sections of everted rat intestines. Clofibrate had no effect on the conversion of acetate-[2-14C] into cholesterol. The results indicate the presence in rat intestine of enzyme systems involved in the saturation of the Δ24-bond in lanosterol and its metabolites, the conversion of 7-dehydrocholesterol into cholesterol, and those inhibited by SKF 525-A. Hence, the pathway of intestinal cholesterol synthesis is similar to that of the liver.
TL;DR: Drawing conclusions regarding the physiological significance of this apparent end product inhibition should be tempered until the process is examined by other experimental approaches.