Biomaterial Database

[Mechanisms of bile acid biosynthesis regulation--autoregulation by bile acids]. 2011

Areta Hebanowska

Gdański Uniwersytet Medyczny, Katedra i Zakład Biochemii, Gdańsk. areta@gumed.edu.pl

Bile acids play significant role in body homeostasis regulation. They are products of cholesterol catabolism and ligands for some nuclear receptors regulating crucial metabolic pathways. The main enzyme regulating bile acids biosynthesis is CYP7A1 (7alpha-cholesterol hydroxylase). Its activity is controlled mainly at the transcription level and the key transcription factor is FXR. It is activated by other nuclear receptors like SHP, HNF-4alpha or LRH-1 and bile acids themselves, and represses CYP7A1 gene. The other transcription factors that inhibit CYP7A1 activity, are PXR, VDR, PPARalpha. The main activator is LXR (in rodents), increasing CYP7A1 transcriptional activity. CYP7A1 activity increases in presence of insulin and glucocorticoids. It is also regulated by diurnal rhythm. Some of those factors influence the activities of other bile acids biosynthesis enzymes--CYP7B1, CYP27A1, CYP8B1. Because of bile acids significant function in body metabolism this article presents the newest knowledge on mechanisms of key enzymes activities control.

UI	MeSH Term	Description	Entries
D002790	Cholesterol 7-alpha-Hydroxylase	A membrane-bound cytochrome P450 enzyme that catalyzes the 7-alpha-hydroxylation of CHOLESTEROL in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP7, converts cholesterol to 7-alpha-hydroxycholesterol which is the first and rate-limiting step in the synthesis of BILE ACIDS.	CYP7,CYP7A,Cytochrome P-450 CYP7,CYP 7,CYP 7A,Cholesterol 7-alpha-Monooxygenase,Cholesterol 7alpha-Hydroxylase,Cholesterol-7-Hydroxylase,Cytochrome P450 7,Cholesterol 7 Hydroxylase,Cholesterol 7 alpha Hydroxylase,Cholesterol 7 alpha Monooxygenase,Cholesterol 7alpha Hydroxylase,Cytochrome P 450 CYP7
D002940	Circadian Rhythm	The regular recurrence, in cycles of about 24 hours, of biological processes or activities, such as sensitivity to drugs or environmental and physiological stimuli.	Diurnal Rhythm,Nyctohemeral Rhythm,Twenty-Four Hour Rhythm,Nycthemeral Rhythm,Circadian Rhythms,Diurnal Rhythms,Nycthemeral Rhythms,Nyctohemeral Rhythms,Rhythm, Circadian,Rhythm, Diurnal,Rhythm, Nycthemeral,Rhythm, Nyctohemeral,Rhythm, Twenty-Four Hour,Rhythms, Circadian,Rhythms, Diurnal,Rhythms, Nycthemeral,Rhythms, Nyctohemeral,Rhythms, Twenty-Four Hour,Twenty Four Hour Rhythm,Twenty-Four Hour Rhythms
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D006706	Homeostasis	The processes whereby the internal environment of an organism tends to remain balanced and stable.	Autoregulation
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001647	Bile Acids and Salts	Steroid acids and salts. The primary bile acids are derived from cholesterol in the liver and usually conjugated with glycine or taurine. The secondary bile acids are further modified by bacteria in the intestine. They play an important role in the digestion and absorption of fat. They have also been used pharmacologically, especially in the treatment of gallstones.	Bile Acid,Bile Salt,Bile Salts,Bile Acids,Acid, Bile,Acids, Bile,Salt, Bile,Salts, Bile