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Bilirubin is conjugated with glucuronic acid in the liver by the enzyme glucuronyltransferase, making it soluble in water. Much of it goes into the bile and thus out into the small intestine. Although 20% of the secreted bilirubinoid bile is reabsorbed by the small intestine, [2] conjugated
In the liver, bilirubin is conjugated with glucuronic acid by the enzyme glucuronyltransferase, first to bilirubin glucuronide and then to bilirubin diglucuronide, making it soluble in water: the conjugated version is the main form of bilirubin present in the "direct" bilirubin fraction. Much of it goes into the bile and thus out into the small ...
The reaction is a transfer of two glucuronic acid groups including UDP glucuronic acid sequentially to the propionic acid groups of the bilirubin, primarily catalyzed by UGT1A1. [ 23 ] [ 24 ] [ 5 ] In greater detail about this reaction, a glucuronosyl moiety is conjugated to one of the propionic acid side chains, located on the C8 and C12 ...
Glucuronidation consists of transfer of the glucuronic acid component of uridine diphosphate glucuronic acid to a substrate by any of several types of UDP-glucuronosyltransferase. UDP-glucuronic acid (glucuronic acid linked via a glycosidic bond to uridine diphosphate) is an intermediate in the process and is formed in the liver.
Depending on the configuration at C-1, there are two anomers of glucuronic acid, α- and β-form. In β-D-glucuronic acid the C-1 hydroxy group is on the same side of the pyranose ring as the carboxyl group. In the free sugar acid, the β-form is prevalent (~64%), whereas in the organism, the α-form UDP-α-D-glucuronic acid (UDPGA) predominates.
The bilirubin-UGT enzyme performs a chemical reaction called glucuronidation. Glucuronic acid is transferred to unconjugated bilirubin, which is a yellowish pigment made when your body breaks down old red blood cells, [35] and then being converted to conjugated bilirubin during the reaction. Conjugated bilirubin passes from the liver into the ...
Once unconjugated bilirubin arrives in the liver, liver enzyme UDP-glucuronyl transferase conjugates bilirubin + glucuronic acid → bilirubin diglucuronide (conjugated bilirubin). Bilirubin that has been conjugated by the liver is water-soluble and excreted into the gallbladder. [citation needed]
Bilirubin is transported into the liver by facilitated diffusion bound to a protein (serum albumin), where it is conjugated with glucuronic acid to become more water-soluble. The reaction is catalyzed by the enzyme UDP-glucuronosyltransferase. [41]