19-401: Uridine 5'-diphospho-glucuronosyltransferase ( UDP -glucuronosyltransferase, UGT ) is a microsomal glycosyltransferase ( EC 2.4.1.17 ) that catalyzes the transfer of the glucuronic acid component of UDP-glucuronic acid to a small hydrophobic molecule. This is a glucuronidation reaction. Alternative names: Glucuronosyltransferases are responsible for the process of glucuronidation ,
38-464: A fused-ring skeletal structure derived of purine , hence they are called purine bases . The purine nitrogenous bases are characterized by their single amino group ( −NH 2 ), at the C6 carbon in adenine and C2 in guanine. Similarly, the simple-ring structure of cytosine, uracil, and thymine is derived of pyrimidine , so those three bases are called the pyrimidine bases . Each of the base pairs in
57-584: A pyrophosphate ion in the process. Then, the enzyme glycogen synthase combines UDP-glucose units to form a glycogen chain. The UDP molecule is cleaved from the glucose ring during this process and can be reused by UDP-glucose pyrophosphorylase. This biochemistry article is a stub . You can help Misplaced Pages by expanding it . Nucleobase Nucleotide bases (also nucleobases , nitrogenous bases ) are nitrogen -containing biological compounds that form nucleosides , which, in turn, are components of nucleotides , with all of these monomers constituting
76-518: A major part of phase II metabolism . Arguably the most important of the Phase II (conjugative) enzymes, UGTs have been the subject of increasing scientific inquiry since the mid-to-late 1990s. The reaction catalyzed by the UGT enzyme involves the addition of a glucuronic acid moiety to xenobiotics and is the most important pathway for the human body's elimination of the most frequently prescribed drugs. It
95-452: A typical double- helix DNA comprises a purine and a pyrimidine: either an A paired with a T or a C paired with a G. These purine-pyrimidine pairs, which are called base complements , connect the two strands of the helix and are often compared to the rungs of a ladder. Only pairing purine with pyrimidine ensures a constant width for the DNA. The A–T pairing is based on two hydrogen bonds , while
114-479: Is a nucleotide diphosphate . It is an ester of pyrophosphoric acid with the nucleoside uridine . UDP consists of the pyrophosphate group , the pentose sugar ribose , and the nucleobase uracil . UDP is an important factor in glycogenesis . Before glucose can be stored as glycogen in the liver and muscles , the enzyme UDP-glucose pyrophosphorylase forms a UDP-glucose unit by combining glucose 1-phosphate with uridine triphosphate , cleaving
133-407: Is also the major pathway for foreign chemical (dietary, environmental, pharmaceutical) removal for most drugs, dietary substances, toxins and endogenous substances. UGT is present in humans, other animals, plants, and bacteria. Famously, UGT enzymes are not present in the genus Felis , and this accounts for a number of unusual toxicities in the cat family. The glucuronidation reaction consists of
152-450: Is required of chemical pathways that permit formation of the key building blocks of life under plausible prebiotic conditions . According to the RNA world hypothesis, free-floating ribonucleotides were present in the primordial soup . These were the fundamental molecules that combined in series to form RNA . Molecules as complex as RNA must have arisen from small molecules whose reactivity
171-558: The bilirubin specific form of glucuronosyltransferase is thought to be the cause of Gilbert's syndrome , which is characterized by unconjugated hyperbilirubinemia . It is also associated with Crigler–Najjar syndrome , a more serious disorder where the enzyme's activity is either completely absent (Crigler–Najjar syndrome type I) or less than 10% of normal (type II). Infants may have a developmental deficiency in UDP-glucuronyl transferase, and are unable to hepatically metabolize
190-497: The genetic code , with the bases A, G, C, and T being found in DNA while A, G, C, and U are found in RNA. Thymine and uracil are distinguished by merely the presence or absence of a methyl group on the fifth carbon (C5) of these heterocyclic six-membered rings. In addition, some viruses have aminoadenine (Z) instead of adenine. It differs in having an extra amine group, creating a more stable bond to thymine. Adenine and guanine have
209-544: The C–G pairing is based on three. In both cases, the hydrogen bonds are between the amine and carbonyl groups on the complementary bases. Nucleobases such as adenine, guanine, xanthine , hypoxanthine , purine, 2,6-diaminopurine , and 6,8-diaminopurine may have formed in outer space as well as on earth. The origin of the term base reflects these compounds' chemical properties in acid–base reactions , but those properties are not especially important for understanding most of
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#1732801998495228-440: The antibiotic drug chloramphenicol which requires glucuronidation. This leads to a condition known as gray baby syndrome . Causes of unconjugated hyperbilirubinemia are divided into three main categories, namely, excessive bilirubin synthesis, liver bilirubin uptake malfunction, and bilirubin conjugation compromise. As to excessive bilirubin synthesis, both intravascular hemolysis and extravascular hemolysis can involve in
247-413: The basic building blocks of nucleic acids . The ability of nucleobases to form base pairs and to stack one upon another leads directly to long-chain helical structures such as ribonucleic acid (RNA) and deoxyribonucleic acid (DNA). Five nucleobases— adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U)—are called primary or canonical . They function as the fundamental units of
266-528: The biological functions of nucleobases. At the sides of nucleic acid structure, phosphate molecules successively connect the two sugar-rings of two adjacent nucleotide monomers, thereby creating a long chain biomolecule . These chain-joins of phosphates with sugars ( ribose or deoxyribose ) create the "backbone" strands for a single- or double helix biomolecule. In the double helix of DNA, the two strands are oriented chemically in opposite directions, which permits base pairing by providing complementarity between
285-607: The genetic code, such as isoguanine and isocytosine or the fluorescent 2-amino-6-(2-thienyl)purine and pyrrole-2-carbaldehyde . In medicine, several nucleoside analogues are used as anticancer and antiviral agents. The viral polymerase incorporates these compounds with non-canonical bases. These compounds are activated in the cells by being converted into nucleotides; they are administered as nucleosides as charged nucleotides cannot easily cross cell membranes. At least one set of new base pairs has been announced as of May 2014. In order to understand how life arose , knowledge
304-673: The many bases created through mutagen presence, both of them through deamination (replacement of the amine-group with a carbonyl-group). Hypoxanthine is produced from adenine, xanthine from guanine, and uracil results from deamination of cytosine. These are examples of modified adenosine or guanosine. These are examples of modified cytidine, thymidine or uridine. A vast number of nucleobase analogues exist. The most common applications are used as fluorescent probes, either directly or indirectly, such as aminoallyl nucleotide , which are used to label cRNA or cDNA in microarrays . Several groups are working on alternative "extra" base pairs to extend
323-521: The pathophysiology. Additionally, dyserythropoiesis and extravasation of blood into tissues such as angioedema and edema can also lead to indirect hyperbilirubinemia, along with heart failure , medication -induced, ethinyl estradiol , chronic hepatitis , and cirrhosis that are, otherwise, attributed to hepatic bilirubin mal-uptake and bilirubin conjugation compromise, respectively. Human genes which encode UGT enzymes include: Uridine-diphosphate Uridine diphosphate , abbreviated UDP ,
342-428: The transfer of the glucuronosyl group from uridine 5'-diphospho-glucuronic acid (UDPGA) to substrate molecules that contain oxygen, nitrogen, sulfur or carboxyl functional groups. The resulting glucuronide is more polar (e.g. hydrophilic) and more easily excreted than the substrate molecule. The product solubility in blood is increased allowing it to be eliminated from the body by the kidneys . A deficiency in
361-527: The two bases, and which is essential for replication of or transcription of the encoded information found in DNA. DNA and RNA also contain other (non-primary) bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytosine (m C). In RNA, there are many modified bases, including those contained in the nucleosides pseudouridine (Ψ), dihydrouridine (D), inosine (I), and 7-methylguanosine (m G). Hypoxanthine and xanthine are two of
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