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Under normal conditions, brain cholesterol is separate from peripheral cholesterol, i.e., the dietary and hepatic cholesterol do not cross the blood brain barrier. Rather, astrocytes produce and distribute cholesterol in the brain. [12] De novo synthesis, both in astrocytes and hepatocytes, occurs by a complex 37-step process.
Cholesterol 24-hydroxylase (EC 1.14.13.98), also commonly known as cholesterol 24S-hydroxylase, cholesterol 24-monooxygenase, CYP46, or CYP46A1, is an enzyme that catalyzes the conversion of cholesterol to 24S-hydroxycholesterol. It is responsible for the majority of cholesterol turnover in the human central nervous system. [1]
24S-HC is an agonist of liver X receptors, a class of nuclear receptors that sense oxysterols. In the brain, liver X receptor beta is the primary LXR type, which interacts with 24S-HC. [5] 24S-HC levels sensed by LXRs can regulate the expression of SREBP mRNA and protein, which in turn regulate cholesterol synthesis and fatty acid synthesis. [8]
Lipid metabolism is the synthesis and degradation of lipids in cells, involving the breakdown and storage of fats for energy and the synthesis of structural and functional lipids, such as those involved in the construction of cell membranes. In animals, these fats are obtained from food and are synthesized by the liver. [1]
CYP27A1 participates in the degradation of cholesterol to bile acids in both the classic and acidic pathways. [5] It is the initiating enzyme in the acidic pathway to bile acids, yielding oxysterols by introducing a hydroxyl group to the carbon at the 27 position in cholesterol.
Cholesterol 7 alpha-hydroxylase is a cytochrome P450 heme enzyme that oxidizes cholesterol in the position 7 using molecular oxygen.It is an oxidoreductase. CYP7A1 is located in the endoplasmic reticulum (ER) and is important for the synthesis of bile acid and the regulation of cholesterol levels.
The protein encoded by this gene is an enzyme catalyzing the production of cholesterol from 7-dehydrocholesterol using NADPH.. The DHCR7 gene encodes delta-7-sterol reductase (EC 1.3.1.21), the ultimate enzyme of mammalian sterol biosynthesis that converts 7-dehydrocholesterol (7-DHC) to cholesterol.
Cholesterol total synthesis in chemistry describes the total synthesis of the complex biomolecule cholesterol and is considered a great scientific achievement. [1] The research group of Robert Robinson with John Cornforth ( Oxford University ) published their synthesis in 1951 [ 2 ] and that of Robert Burns Woodward with Franz Sondheimer ...