UGT2B7

Key takeaways

UGT2B7 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect UGT2B7 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of UGT2B7 from memory before moving on to harder problems.

Reference excerpt

UGT2B7 (UDP-Glucuronosyltransferase-2B7) is a phase II metabolism isoenzyme found to be active in the liver, kidneys, epithelial cells of the lower gastrointestinal tract and also has been reported in the brain. In humans, UDP-glucuronosyltransferase-2B7 is encoded by the UGT2B7 gene.

Structure

Human UGT2B7 is a membrane-associated enzyme that functions as a dimer, with each monomer contributing to the overall structural and catalytic architecture. Although a full-length structure of any human UGT has not yet been resolved, the available structural information from the C-terminal domain reveals key features of the protein. This region forms two interacting domains, each adopting a Rossman-like fold characteristic of nucleotide-binding proteins. The Rossmann fold mediates binding of the UDP-glucuronic acid cofactor required for glucuronidation. Consistent with this role, the C-terminus of UGT enzymes is highly conserved and specialized for cofactor binding, whereas the structurally unresolved N-terminus is responsible for substrate recognition and specificity. Dimerization is an intrinsic structural feature of UGT2B7 and influences its functional state. The resolved C-terminal structure suggests that interactions between monomers can position the C-terminus of one subunit within the UDP-glucuronic acid binding site of the partner subunit, potentially modulating catalytic competence. UGT2B7 can form both homodimers and heterodimers with other UGT isoforms, including UGT1A1, as well as with its own genetic variants. These oligomeric arrangements alter the structural organization of the enzyme and can impact glucuronidation activity depending on the specific pairing.

Function The UGTs serve a major role in the conjugation and subsequent elimination of potentially toxic xenobiotics and endogenous compounds. UGT2B7 has unique specificity for 3,4-catechol estrogens and estriol, suggesting that it may play an important role in regulating the level and activity of these potent estrogen metabolites. This enzyme is located on the endoplasmic reticulum and nuclear membranes of cells. Its function is to catalyse the conjugation of a wide variety of lipophilic aglycon substrates with glucuronic acid, using uridine diphosphate glucuronic acid. Together with UGT2B4, UGT2B7 is capable of glucosidation of hyodesoxycholic acid in the liver, but, unlike the 2B4 isoform, 2B7 is also able to glucuronidate various steroid hormones (androsterone, epitestosterone) and fatty acids. It is also able to conjugate major classes of drugs such as analgesics (morphine), carboxylic nonsteroidal anti-inflammatory drugs (ketoprofen), and anticarcinogens (all-trans retinoic acid). UGT2B7 is the major enzyme isoform responsible for the metabolism of morphine, codeine, norcodeine and other opiates to their corresponding 3- and 6- glucuronides. For example, morphine metabolism produces morphine-3-glucuronide (M3G), which has no analgesic effect, by adding a sugar acid at the phenolic hydroxy group, with uridine diphosphate (UDP) as byproduct:

Morphine-6-glucuronide (M6G) is produced in a similar reaction and has analgesic effects more potent than morphine. As a consequence, altered UGT2B7 activity can significantly affect both the effectiveness and side-effects of morphine, as well as some related opiate drugs.

Genetic polymorphism UGT2B7 is considered to be a highly polymorphic gene. Various research efforts have investigated the potential effect of these polymorphic variants on glucuronidation activity of UGT2B7 and especially its clearance of administered drugs, including anticancer therapies. Decreased glucuronidation activity by genetically variant UGT2B7 could lead to increased toxicity due to elevated levels of the drug remaining or accumulating in a patient's organs especially liver, while increased activity could mean lower efficacy of the administered therapy due to lower than expected levels in the body. One study found that Han Chinese dye-industry workers exposed to benzidine were at higher risk for developing bladder cancer if they had the UGT2B7 single nucleotide polymorphism (SNP) C802T encoding His268Tyr. The histidine to tyrosine mutation at residue 268 is located in the N-terminal portion of UGT2B7, which binds the xenobiotic substrate as opposed to the C-terminus which binds UDP-glucuronic acid. The speculated mechanism for this increased cancer risk involved increased glucuronidation of benzidine by the mutant UGT2B7 followed by cleavage of the glucuronidated benzidine at urine pH levels, releasing higher concentrations of benzidine in the bladder. Another study looked for a similar association of variant UGT2B7 G900A with the risk of colorectal cancer but found no significant association. A study of erlotinib clearance in non-small cell lung cancer patients showed no statistical significance for SNPs of UGT2B7, which potentially metabolizes erlotinib as indicated by erlotinib inhibition of UGT2B7. An investigation into the clearance of diclofenac, a nonsteroidal anti-inflammatory drug (NSAID) that can cause serious drug-induced liver injury, showed that mutant UGT2B7 with the C802T SNP had a 6-fold lower clearance of diclofenac than wild-type UGT2B7, possibly contributing to increased liver toxicity in patients with this mutation. Analysis of genetic polymorphisms of UGT2B7 in anti-tuberculosis drug-induced liver injury (ATLI) found no association between mutations of UGT2B7 and ATLI in the studied population. UGT2B7 is also known to be involved in the metabolism of opioids via glucuronidation, and a study investigating the effect of polymorphisms on the analgesic efficacy of buprenorphine found that the mutation C802T significantly worsened the analgesic response to buprenorphine after thoracic surgery, particularly at longer time-points (48 hours) where this long-lasting opioid is meant to remain effective. This same variant was found separately to have significant effects on the blood plasma concentration of valproic acid administered to epilepsy patients, which may account for some of the individual variability seen with this narrow-therapeutic window treatment. Both of these cases indicate decreased concentrations of drug compound probably due to increased glucuronidation activity of UGT2B7 with the C802T polymorphism.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with UGT2B7

Start with the simplest possible case. Write down what UGT2B7 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to UGT2B7 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about UGT2B7 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of UGT2B7

In research: UGT2B7 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses UGT2B7 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: UGT2B7 is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 2.4.1, Genes on human chromosome 4, Transferases, so understanding it makes those chapters shorter.
In everyday life: Look for UGT2B7 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study UGT2B7 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what UGT2B7 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain UGT2B7 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is UGT2B7 in simple terms?

UGT2B7 (UDP-Glucuronosyltransferase-2B7) is a phase II metabolism isoenzyme found to be active in the liver, kidneys, epithelial cells of the lower gastrointestinal tract and also has been reported in the brain. In humans, UDP-glucuronosyltransferase-2B7 is encoded by the UGT2B7 gene.

Why does UGT2B7 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study UGT2B7?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on UGT2B7.