What does cholesterol 7 alpha-hydroxylase do?
Cholesterol 7 alpha-hydroxylase (7 alpha-hydroxylase) is the rate-limiting enzyme in bile acid biosynthesis. It is subject to a feedback control, whereby high levels of bile acids suppress its activity, and cholesterol exerts a positive control.
Where can cholesterol be metabolized by 7 alpha-hydroxylase?
bile acids
I. Cholesterol 7 α-hydroxylase catalyses the first reaction in the metabolism of cholesterol to the primary bile acids, cholic acid and chenodeoxycholic acid.
What is the function of 7α hydroxylase?
Cholesterol 7α-hydroxylase is a rate-limiting enzyme in bile acid synthesis and plays an important role in maintaining cholesterol homeostasis in the body. The CYP7A1 −204A/C polymorphism in the regulatory region of the gene plays an important role in the determination of individual responses to dietary changes.
How is 7alpha hydroxylase regulated?
Cholesterol-7alpha-hydroxylase (CYP7A1) regulates the pathway through which cholesterol is converted into bile acids. Bile acid activation of FXR has been shown to repress the expression of CYP7A1 via increasing the expression of small heterodimer partner (SHP), a non-DNA binding protein.
What are fibrates used for?
Fibrates are medicines prescribed to help lower high triglyceride levels. Triglycerides are a type of fat in your blood. Fibrates also may help raise your HDL (good) cholesterol. High triglycerides along with low HDL cholesterol increase the risk of heart disease and stroke.
What is bile acid metabolism?
Bile acid metabolism is inexorably linked to cholesterol and phospholipid metabolism in humans. Bile acids are cholesterol metabolites. The rate-limiting step is hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase, which is regulated by serum bile acid concentration from the enterohepatic circulation.
What is metabolism of cholesterol?
LDL particles contain a core of cholesterol esters and a smaller amount of triglyceride. LDL is internalized by hepatic and nonhepatic tissues. In the liver, LDL is converted into bile acids and secreted into the intestines. In non hepatic tissues, LDL is used in hormone production, cell membrane synthesis, or stored.
What are primary and secondary bile acids?
Primary bile acids are those synthesized by the liver. Secondary bile acids result from bacterial actions in the colon. Bile acids comprise about 80% of the organic compounds in bile (others are phospholipids and cholesterol). An increased secretion of bile acids produces an increase in bile flow.
Which is the hydroxylation reaction in cholesterol synthesis?
Enzymatic mechanism The enzyme cholesterol 7 alpha hydroxylase catalyzes the reaction that converts cholesterol into cholesterol 7 alpha hydroxylase reducing and oxidizing that molecule.
What are fibrates for cholesterol?
How do fibrates reduce LDL?
Fibrate treatment results in the formation of LDL with a higher affinity for the LDL receptor, which are thus catabolized more rapidly. 4. Reduction in neutral lipid (cholesteryl ester and triglyceride) exchange between VLDL and HDL may result from decreased plasma levels of TRL.
What is the role of cholesterol 7 alpha hydroxylase?
Cholesterol 7 alpha hydroxylase (CYP7A1) is a rate-limiting enzyme for cholesterol catabolism and bile acid synthesis. One study reported that CC genotype as well as the C allele of CYP7A1 A204C polymorphism conferred high risk for GBC.
How is cholesterol 7 related to oxysterol 7?
According to current theories, cholesterol 7 alpha-hydroxylase (CYP7A) is responsible for the former and oxysterol 7 alpha-hydroxylase (CYP7B) for the latter reaction. CYP7A is believed to have a very high substrate specificity whereas CYP7B is active toward oxysterols, dehydroepiandrosterone, and pregnenolone.
Which is the first reaction of cholesterol 7?
Cholesterol 7 α-hydroxylase catalyses the first reaction in the metabolism of cholesterol to the primary bile acids, cholic acid and chenodeoxycholic acid.
Which is the enzyme that synthesizes cholesterol into bile acid?
Cholesterol 7 alpha-hydroxylase is the rate-limiting enzyme in the synthesis of bile acid from cholesterol via the classic pathway, catalyzing the formation of 7α-hydroxycholesterol. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients.