Concept explainers
Interpretation:
Mechanisms for the three steps involved in the conversion of 3-phosphoglycerate into glyceraldehyde-3-phosphate, 1) Phosphorylation of 3-phosphoglycerate by treating with ATP to form 1,3- bisphosphoglycerate.2) Reaction of 1,3- bisphosphoglycerate with the thiol group on the enzyme to give an enzyme-bound thioester 3) Reduction of the enzyme bound thioester with NADH, are to be proposed.
Concept introduction:
All the three steps involved in the conversion of 3-phosphoglycerate into glyceraldehyde-3-phosphate take place through two steps i) Attack of a nucleophile on either P or C and ii) Elimination of the leaving group.
To propose:
Mechanisms for the three steps involved in the conversion of 3-phosphoglycerate into glyceraldehyde-3-phosphate 1) Phosphorylation of 3-phosphoglycerate by treating with ATP to form 1,3- bisphosphoglycerate 2) Reaction of 1,3- bisphosphoglycerate with the thiol group on the enzyme to give an enzyme-bound thioester 3) Reduction of the enzyme bound thioester with NADH.
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Chapter 21 Solutions
ORGANIC CHEM.(LL)-W/OWL V2 >CUSTOM<
- One of the steps in the pentose phosphate pathway for glucose catabolism is the reaction of sedoheptulose 7-phosphate with glyceraldehydes 3-phosphate in the presence of a transaldolase to yield erythrose 4-phosphate and fructose 6-phosphate. (a) The first part of the reaction is the formation of a protonated Schiff base of sedoheptulose 7-phosphate with a lysine residue in the enzyme followed by a retro-aldol cleavage to give an enamine plus erythrose 4-phosphate. Show the structure of the enamine and the mechanism by which it is formed. (b) The second part of the reaction is a nucleophilic addition of the enamine to glyceraldehyde 3-phosphate followed by hydrolysis of the Schiff base to give fructose 6-phosphate. Show the mechanism.arrow_forwardOne of the later steps in glucose biosynthesis is the isomerization of fructose 6-phosphate to glucose 6-phosphate. Propose a mechanism, using acid or base catalysis as needed.arrow_forwardIn dilute aqueous base, (R)-glyceraldehyde is converted into an equilibrium mixture of (R,S)-glyceraldehyde and dihydroxyacetone. Propose a mechanism for this isomerization.arrow_forward
- One of the steps in the biosynthesis of uridine monophosphate is the reaction of aspartate with carbamoyl phosphate to give carbamoyl aspartate followed by cyclization to form dihydroorotate. Propose mechanisms for both steps.arrow_forwardTreatment of -D-glucose with methanol in the presence of an acid catalyst converts it into a mixture of two compounds called methyl glucosides (Section 25.3A). In these representations, the six-membered rings are drawn as planar hexagons. (a) Propose a mechanism for this conversion and account for the fact that only the OH on carbon 1 is transformed into an OCH3 group. (b) Draw the more stable chair conformation for each product. (c) Which of the two products has the chair conformation of greater stability? Explain.arrow_forwardThe formation of Br2 from NBS first involves the reaction of NBS with HBr to form an iminol intermediate and molecular bromine. The intermediate then undergoes acid-catalyzed tautomerism to form succinimide, the byproduct of the reaction. Propose a curved-arrow mechanism for the conversion of NBS into succinimide that also accounts for the formation of Br2.arrow_forward
- Ethanolamine ammonia lyase, a coenzyme B12–requiring enzyme, catalyzes the following reaction. Propose a mechanism for this reaction.arrow_forwardWhen the gum of the shrub Sterculia setigera is subjected to acidic hydrolysis, one of the water-soluble components of thehydrolysate is found to be tagatose. The following information is known about tagatose:(1) Molecular formula C6H12O6(2) Undergoes mutarotation.(3) Does not react with bromine water.(4) Reduces Tollens reagent to give d-galactonic acid and d-talonic acid.(5) Methylation of tagatose (using excess CH3 I and Ag2O) followed by acidic hydrolysis gives1,3,4,5-tetra-O-methyltagatose.(a) Draw a Fischer projection structure for the open-chain form of tagatose.(b) Draw the most stable conformation of the most stable cyclic hemiacetal form of tagatosearrow_forwardPropose a synthesis pathway and reagents for the preparation of the following compound. (+/-) indicates a racemic connectionarrow_forward
- The most stable conformation of most aldopyranoses is one in which the largest group, the CH2OH group, is equatorial. However, alpha-D-idopyranose exists primarily in a conformation with an axial CH2OH group. Write formulas for the two chair conformations of a-D-idopyranose (one with the CH2OH group axial and one with the CH2OH group equatorial) and provide an explanationarrow_forwardGive explanation for the following fact:- The enzyme alcohol dehydrogenase catalyzes the oxidation of CH3CH2OH to CH3CHO. But when racemic CH3CHDOH is similarly oxidized, an optically active enantiomer remains.arrow_forwardd-Glucuronic acid is found widely in plants and animals. One of its functions is to detoxify poisonous HO-containing compoundsby reacting with them in the liver to form glucuronides. Glucuronides are water soluble and therefore readily excreted. Afteringestion of a poison such as turpentine or phenol, the glucuronides of these compounds are found in the urine. Draw thestructure of the a- and b-glucuronides formed by the reaction of b-d-glucuronic acid and phenol.arrow_forward
- Introduction to General, Organic and BiochemistryChemistryISBN:9781285869759Author:Frederick A. Bettelheim, William H. Brown, Mary K. Campbell, Shawn O. Farrell, Omar TorresPublisher:Cengage LearningOrganic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning