Muricholic acids are a group of

bile acid Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver. Bile acids are conjugated with taurine or glycine residues to give anions called bile salts. Primary b ...

s found as one of the main forms in

mice A mouse ( : mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

, which gives them their name, and at low concentrations in other species. Muricholic acids differ from the primary bile acids found in humans,

cholic acid Cholic acid, also known as 3α,7α,12α-trihydroxy-5β-cholan-24-oic acid is a primary bile acid that is insoluble in water (soluble in alcohol and acetic acid), it is a white crystalline substance. Salts of cholic acid are called cholates. Ch ...

and

chenodeoxycholic acid Chenodeoxycholic acid (CDCA; also known as chenodesoxycholic acid, chenocholic acid and 3α,7α-dihydroxy-5β-cholan-24-oic acid) is a bile acid. Salts of this carboxylic acid are called chenodeoxycholates. Chenodeoxycholic acid is one of the mai ...

, by having a

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

in the β- configuration at the 6-position. The orientation of the hydroxyl group at the 7 position defines α- or β-muricholic acid. Muricholic acids are detectable at low concentrations in human urine. The three major bile acids in germ-free mice are cholic acid, α-muricholic, and β-muricholic acids. In conventional mice with a normal

microbiome A microbiome () is the community of microorganisms that can usually be found living together in any given habitat. It was defined more precisely in 1988 by Whipps ''et al.'' as "a characteristic microbial community occupying a reasonably well ...

, ω-muricholic acid, and various sulfated forms are also found.

Conjugation Conjugation or conjugate may refer to: Linguistics * Grammatical conjugation, the modification of a verb from its basic form * Emotive conjugation or Russell's conjugation, the use of loaded language Mathematics * Complex conjugation, the chang ...

with

taurine Taurine (), or 2-aminoethanesulfonic acid, is an organic compound that is widely distributed in animal tissues. It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight. It ...

(to give tauromuricholic acids which are the main forms), or with

glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinogeni ...

(to give glycomuricholic acids) takes place in the liver before secretion. The enzyme responsible for the 6-hydroxylation reactions forming muricholates in rodents is the

cytochrome P450 Cytochromes P450 (CYPs) are a Protein superfamily, superfamily of enzymes containing heme as a cofactor (biochemistry), cofactor that functions as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are ...

''Cyp2c70''. This produces α-muricholic acid from chenodeoxycholic acid, and β-muricholic acid from

ursodeoxycholic acid Ursodeoxycholic acid (UDCA), also known as ursodiol, is a secondary bile acid, produced in humans and most other species from metabolism by intestinal bacteria. It is synthesized in the liver in some species, and was first identified in bile of ...

. Tauromuricholic acids were shown to be potent antagonists of the bile acid receptor

farnesoid X receptor The bile acid receptor (BAR), also known as farnesoid X receptor (FXR) or NR1H4 (nuclear receptor subfamily 1, group H, member 4), is a nuclear receptor that is encoded by the ''NR1H4'' gene in humans. Function FXR is expressed at high levels ...

(FXR).

Chemical structures

File:alpha-muricholic acid.svg, α-muricholic acid File:beta-muricholic acid.svg, β-muricholic acid File:gamma-muricholic acid.svg, γ-muricholic acid (hyocholic acid) File:omega-muricholic acid.svg, ω-muricholic acid

References

{{Reflist Bile acids Cholanes