Concept explainers
A student is trying to determine the mechanism for a reaction that uses ATP to activate a carboxylate ion, which then reacts with a thiol. If the carboxylate ion attacks the γ-phosphorous of ATP, the reaction products are the thioester, ADP, and phosphate. However, whether it attacks the α-phosphorus or the β-phosphorus of ATP cannot be determined from the reaction products because the thioester, AMP, and pyrophosphate would be the products in both reactions. The mechanisms can be distinguished by a labeling experiment in which the enzyme, the carboxylate ion, ATP, and radioactively labeled pyrophosphate are incubated and then the ATP is isolated. If the isolated ATP is radioactive, attack occurred on the α-phosphorous. If it is not radioactive, then attack occurred on the β-phosphorous. Explain these conclusions.
Want to see the full answer?
Check out a sample textbook solutionChapter 24 Solutions
Organic Chemistry (8th Edition)
- In this section of the course, you have come across two drugs which inhibit dihydrofolate reductase. One of thes drugs is used as an antibacterial drug and the other is used in treatment of cancer. Why is it that each of these drugs can only be used for one purpose (and not the other) in clinical medicine.arrow_forwardDraw the complete, step-wise mechanism of a phosphate transfer reaction that follows a concerted pathway or SN2 type reaction pathway. Clearly depict the transition state of the reaction.. R₁ B: ti R2 ertarrow_forwardPlease draw by hand. Triosephosphate isomerase (TIM) catalyzes the conversion of dihydroxyacetone phosphate to glyceraldehyde-3-phosphate. The enzyme's catalytic groups are Glu 165 and His 95. In the first step of the reaction, these catalytic groups function as a base and an acid catalyst, respectively. Propose a mechanism for the reaction. ОН 2-03Р0 ОН dihydroxyacetone phosphate triosephosphate isomerase 2-03РО. H glyceraldehyde-3-phosphate FYI Glu is glutamic acid and his is histadinearrow_forward
- Human xanthine oxidase catalyzes the oxidation of hypoxanthine to xanthine and can further catalyze the oxidation of xanthine to uric acid. For the treatment of hyperuricemia and gout, several medications are used to inhibit the activity of xanthine oxidase and reduce the production of uric acid. You are a biochemist and just discovered a chemical that can inhibit the activity of the human xanthine oxidase. When analyzing its mode of inhibition, you found that the enzyme inhibitor complex requires 450 J/mol to dissociate and that it displays kinetics somehow similar to noncompetitive inhibition. You sent your inhibitor to the ministry of health for approval as a medication for gout. Based on the data provided, are they going to authorize it as a medication or not? Explain?arrow_forwardNeostigmine is an inhibitor of acetylcholinesterase. The enzyme attempts to catalyse the same reaction on neostigmine as it does with acetylcholine. However, a stable intermediate is formed which prevents completion of the process and which results in a molecule being covalently linked to the active site. Identify (draw) the stable intermediate and explain why it is stable.arrow_forwardThe correct expression for the autoprotolysis of H20 is H3O+ + H2O = H30* + OH OH- + H,O = H30* + OH 2H20 = H30* + OH 2H20 2H30* H20 = H30* + OHarrow_forward
- The enzyme that catalyzes reaction below can be classified as: NAD* NADH + H* Но- H-Ć- Н—с—н H- malate dehydrogenase Oxaloacetate Malatearrow_forwardIn PLP-catalyzed reactions, the bond broken in the substrate molecule must be perpendicular to the plane of the pyridinium ring. Considering the bonds present in this ring, describe why this arrangement stabilizes the carbanion.arrow_forwardDefine acetylcholinesterasearrow_forward
- Give the name of the enzyme that will most likely catalyze each of the following reactions: O CH3 - CH2 - OH + NAD+ → CH3 – C – H + NADH + H+ Ans. ___________________________________________ CH3 – C – COOH + R – CH – COOH → CH3 – CH – COOH + R – C – COOH O NH2 NH2 O HO – C – CH – CH2 – C – OH → HO – C – CH = CH – C – OH + H2O O OH O O O CO2 + CH3 – C – C – OH + ATP → HO – C – CH2 – C – C – OH + ADP + Pi O O O O…arrow_forwardIn the glycolytic pathway, a six-carbon sugar (fructose 1,6-bisphosphate) is cleaved to form two three-carbon sugars, which undergo further metabolism . In this pathway, an isomerization of glucose 6-phosphate tofructose 6-phosphate (shown below) occurs two steps before the cleavage reaction (the intervening step is phosphorylation of fructose 6-phosphate to fructose 1,6-bisphosphate ). What does the isomerization step accomplish from a chemical perspective? (Hint: Consider what might happen if the C—C bond cleavage were to proceed without the preceding isomerization.)arrow_forwardDescribe the reactions that you would expect these enzymes to catalyze.(a) Alcohol dehydrogenase (b) Aspartate transaminase(c) Tyrosine-tRNA synthetase (d) Phosphohexose isomerasearrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage LearningGeneral, Organic, and Biological ChemistryChemistryISBN:9781285853918Author:H. Stephen StokerPublisher:Cengage LearningOrganic And Biological ChemistryChemistryISBN:9781305081079Author:STOKER, H. Stephen (howard Stephen)Publisher:Cengage Learning,
- Chemistry for Today: General, Organic, and Bioche...ChemistryISBN:9781305960060Author:Spencer L. Seager, Michael R. Slabaugh, Maren S. HansenPublisher:Cengage Learning