UGT2B4
Encyclopedia
UDP glucuronosyltransferase 2 family, polypeptide B4, also known as UGT2B4, is an enzyme
that in humans is encoded by the UGT2B4 gene
.
of hyodeoxycholic acid
, a bile acid
, and catechol-estrogen
s, such as 17-epiestriol and 4-hydroxy-estrone
.
The expression of the UGT2B4 enzyme is upregulated by the farnesoid X receptor
(FXR), a nuclear receptor
which is activated by bile acids. These same bile acids are substrates for the UGT2B4 enzyme. Hence upregulation of UGT2B4 by activated FXR provides a mechanism for the detection, conjugation and subsequent elimination of toxic bile acids.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that in humans is encoded by the UGT2B4 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
.
Function
UGT2B4 is mainly involved in the glucuronidationGlucuronidation
Glucuronidation is the addition of glucuronic acid to a substrate. Glucuronidation is often involved in xenobiotic metabolism of substances such as drugs, pollutants, bilirubin, androgens, estrogens, mineralocorticoids, glucocorticoids, fatty acid derivatives, retinoids, and bile acids...
of hyodeoxycholic acid
Hyodeoxycholic acid
Hyodeoxycholic acid, also known as 3α,6α-Dihydroxy-5β-cholan-24-oic acid or HDCA, is a secondary bile acid, one of the metabolic byproducts of intestinal bacteria. It differs from deoxycholic acid in that the 6α-hydroxyl is in the 12 position in the former. The 6α-hydroxyl group makes HDCA a...
, a bile acid
Bile acid
Bile acids are steroid acids found predominantly in the bile of mammals. Bile salts are bile acids compounded with a cation, usually sodium. In humans, the salts of taurocholic acid and glycocholic acid represent approximately eighty percent of all bile salts. The two major bile acids are cholic...
, and catechol-estrogen
Estrogen
Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...
s, such as 17-epiestriol and 4-hydroxy-estrone
Estrone
Estrone is an estrogenic hormone secreted by the ovary as well as adipose tissue.Estrone is one of several natural estrogens, which also include estriol and estradiol...
.
The expression of the UGT2B4 enzyme is upregulated by the farnesoid X receptor
Farnesoid X receptor
The bile acid receptor , also known as farnesoid X receptor or NR1H4 is a nuclear receptor that is encoded by the NR1H4 gene in humans.- Function :...
(FXR), a nuclear receptor
Nuclear receptor
In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules...
which is activated by bile acids. These same bile acids are substrates for the UGT2B4 enzyme. Hence upregulation of UGT2B4 by activated FXR provides a mechanism for the detection, conjugation and subsequent elimination of toxic bile acids.