نتایج جستجو برای: 22 dehydrocholesterol
تعداد نتایج: 212275 فیلتر نتایج به سال:
The mechanism for the catalytic reduction of the double bond at C-7, 8 in 7-dehydrocholesterol by 3beta-hydroxysterol Delta7-reductase was investigated by testing structurally related sterols as substrates and potential inhibitors. The hepatic smooth endoplasmic reticulum was identified as the site of enzyme activity. All putative substrates contained 27 carbons, but differed from 7-dehydrochol...
Changes in plasma 25-hydroxyvitamin D (25-OHD) were used as an index of vitamin D status of cats. Plasma 25-OHD concentration of kittens given a purified vitamin D-free diet and exposed to direct summer sun for 15 h/wk declined at a similar rate as kittens given the same diet kept indoors. Similarly, plasma 25-OHD of kittens exposed to ultraviolet (UV) lamps declined at a similar rate as kitten...
In a classical sense, vitamin D3, the form produced in animals, is not a true “vitamin” because it is produced in the skin from 7-dehydrocholesterol by UV radiation in the range 290 to 300 nm; 7-dehydrocholesterol is produced from cholesterol metabolism. Only when exposure to sunlight is inadequate does vitamin D3 become a vitamin in the historical sense. Further, vitamin D3 is now termed a pro...
Maintaining redox balance is critical for the production of heterologous secondary metabolites, whereas on various occasions the native cofactor balance does not match the needs in engineered microorganisms. In this study, 7-dehydrocholesterol (7-DHC, a crucial precursor of vitamin D3) biosynthesis pathway was constructed in Saccharomyces cerevisiae BY4742 with endogenous ergosterol synthesis p...
Smith–Lemli–Opitz syndrome (SLOS) is an inborn error of metabolism for cholesterol synthesis. The enzyme defect involved in the syndrome is mutation of 7-Dehydrocholesterol reductase (DHCR7) which leads to increase in plasma concentration of 7and 8-dehydrocholesterol (DHC) levels. The affected patients have different presentation and usually involve all systems of the body. We report a newborn ...
The photosynthesis of previtamin D3 from 7-dehydrocholesterol in human skin was determined after exposure to narrow-band radiation or simulated solar radiation. The optimum wavelengths for the production of previtamin D3 were determined to be between 295 and 300 nanometers. When human skin was exposed to 295-nanometer radiation, up to 65 percent of the original 7-dehydrocholesterol content was ...
Since 1934, when it was shown that ergosterol is not the only provitamin D occurring in nature (l), the provitamin D content of the mixed sterols from many sources has been investigated (2-6). It has been found that the sterols from many of the invertebrates contain a surprisingly large amount of provitamin D as measured spectroscopically. Windaus (3) and Bock and Wetter (4) were able to isolat...
Smith-Lemli-Opitz/RSH syndrome (SLOS), a relatively common birth-defect mental-retardation syndrome, is caused by mutations in DHCR7, whose product catalyzes an obligate step in cholesterol biosynthesis, the conversion of 7-dehydrocholesterol to cholesterol. A null mutation in the murine Dhcr7 causes an identical biochemical defect to that seen in SLOS, including markedly reduced tissue cholest...
It was confirmed that delta 5,7-sterol delta 7-reductase activity was suppressed by cholecalciferol (vitamin D3) in the enzyme system consisted of microsomes and sterol carrier protein (SCP). The enzyme activity was significantly decreased in the combination with microsomes obtained from either vitamin D-deficient or vitamin D3-treated rat liver and with SCP obtained from vitamin D3-treated rat...
Thirty years after its clinical delineation in humans and its teratologic simulation in rats, a Garrodian error of metabolism was discovered in the autosomal recessive RSH/SLO syndrome, namely defective conversion of 7-dehydrocholesterol to cholesterol due to the mutant 7-dehydrocholesterol reductase. This opened the door to the study of several other defects of sterol biosynthesis in humans an...
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