Search results
Results from the WOW.Com Content Network
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]
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]
About 80% of total daily cholesterol production occurs in the liver and the intestines; [37] other sites of higher synthesis rates include the brain, the adrenal glands, and the reproductive organs. Synthesis within the body starts with the mevalonate pathway where two molecules of acetyl CoA condense to form acetoacetyl-CoA.
Besides its role in the synthesis of ketone bodies, HMG-CoA is also an intermediate in the synthesis of cholesterol, but the steps are compartmentalised. [1] [2] Ketogenesis occurs in the mitochondria, whereas cholesterol synthesis occurs in the cytosol, hence both processes are independently regulated. [2]
Expression of the recombinant protein demonstrated 7alpha-hydroxylation activity for steroids (DHEA, pregnenolone) and oxysterols including 25-hydroxycholesterol and 27-hydroxycholesterol, [9] [10] [11] confirmed by knockout in mouse that abolished oxysterol hydroxylation in liver [12] and brain and steroid hydroxylation in multiple tissues. [13]
Cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid [2] and vitamin D. In mammals cholesterol is either absorbed from dietary sources or is synthesized de novo. Up to 70-80% of de novo cholesterol synthesis occurs in the liver, and about 10% of de novo cholesterol synthesis occurs in the small intestine. [3]
Cholesterol synthesis Woodward 1 Acid 19 was converted to lactone 20 ( acetic anhydride , sodium acetate ) and reaction with methylmagnesium chloride gave tetracyclic ketone 21 . Treatment with periodic acid (dioxane) and piperidine acetate (benzene) gave aldehyde 24 through diol 22 (oxidation) and dialdehyde 23 (aldol condensation).
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.