Concept explainers
Interpretation:
Given that galactose is
Concept introduction:
UDP-Galactose has an axial –OH on C4 while UDP-glucose has it in equatorial position. The isomerization of UDP-galactose to UDP-glucose can be brought about by oxidizing the -OH on C4 in to a
To propose:
A mechanism for the isomerization of UDP-galactose to UDP-glucose where UDP is uridylyl diphosphate. The enzyme responsible for the transformation uses NAD+ as cofactor.
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Organic Chemistry
- 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_forwardPropose a mechanism for the biosynthesis of the sesquiterpenoid trichodiene from farnesyl diphosphate. The process involves cyclization to give an intermediate secondary carbocation, followed by several carbocation rearrangements.arrow_forward
- Prostaglandins are a class of cicosanoids, fatty acid derivatives with a variety of extremely potent actions on vertebrate tissues. They are responsible for producing fever and inflammation and its associated pain. Prostaglandins are derived from the 20- carbon fatty acid arachidonic acid in a reaction catalyzed by the enzyme prostaglandin endoperoxide synthase. This enzyme, a cyclooxygenase, uses oxygen to convert arachidonic acid to PGG2, the immediate precursor of many different prostaglandins. Rate of formation of PGG2 with 10 mg/ml ibuprofen (mM/min) Arachidonic acid (mM) Rate of formation of PGG2 (mM/min) 0.190 12.3 0.228 13.9 0.342 17.5 0.570 1.33 22.2 28.8 7.71 8.88 11.9 16.3 24.0 The kinetic data given in the table are for the reaction catalyzed by a mutant of prostaglandin endoperoxide synthase. Focusing here on the first two columns, determine the Vmax and Km of the enzyme. Vmax = Km mM/min mMarrow_forwardA variation of the acetamidomalonate synthesis can be used to synthesize serine. The process involves the following steps: Ethoxide ion deprotonates diethyl acetamidomalonate, forming enolate anion 1; Enolate anion 1 makes a nucleophilic attack on formaldehyde, forming tetrahedral intermediate 2; Protonation of the oxyanion forms alcohol 3; Acid hydrolysis yields dicarboxyamino alcohol 4; Decarboxylation leads to the final amino acid. Write out the mechanism on a separate sheet of paper, and then draw the structure of tetrahedral intermediate 2. You do not have to consider stereochemistry. You do not have to explicitly draw H atoms. Do not include lone pairs in your answer. They will not be considered in the grading. Draw carboxyl and amino groups in their uncharged forms.arrow_forwardProstaglandins are a class of eicosanoids, fatty acid derivatives involved in a variety of important phenomena, including fever, inflammation, and pain. The first step in prostaglandin synthesis involves the conversion of the 20-carbon fatty acid arachidonic acid to PGG2 by the enzyme prostaglandin endoperoxide synthase, or cyclooxy: Ibuprofen is one of several inhibitors of cyclooxogenase used therapeutically. Arachidonic acid 20₂ 0.5 1.0 1.5 2.5 3.5 cyclooxrygenase PGG₂ JOH محمد The following kinetic data were obtained for the enzyme cyclooxygenase in the absence of any inhibitor (1), and in the presence of ibuprofen (2) at a concentration of 48 [arachidonic acid] (uM) (1) v(uM/min) (2) v(uM/min) 23.5 32.2 36.9 41.8 44.0 16.67 25.25 30.49 37.04 38.91 Ibuprofen A. Plot the data in standard Michaelis-Menten form as well as in double-reciprocal form. B. Determine Vmax and Km for the enzyme. C. Based on this limited data set, what type of inhibition does ibuprofen likely exhibit?…arrow_forward
- When dichloromethane is treated with strong NaOH, an intermediate is generated that reacts like a carbene. Draw the structure of this reactive intermediate, and propose a mechanism for its formation.arrow_forwardLook up the structure of lisdexamfetamine (Vyvanse), a drug used in the treatment of attention deficit hyperactivity disorder (ADHD). Redraw it and identify all the functional groups present. What is known about itstherapeutic properties?arrow_forwardA graduate student was studying enzymatic reductions of cyclohexanones when she encountered some interesting chemistry. When she used an enzyme and NADPH to reduce the following ketone, she was surprised to find that the product was optically active. She carefully repurified the product so that no enzyme, NADPH, or other contaminants were present. Still, the product was optically active. Is the product capable of showing optical activity? If it is, explain how.arrow_forward
- y-Butyrolactone (C4H6O2, GBL) is a biologically inactive compound that is converted to the biologically active recreational drug GHB (Section 19.5) by a lactonase enzyme in the body. Since y-butyrolactone is more fat soluble than GHB, it is more readily absorbed by tissues and thus produces a faster onset of physiological symptoms. y-Butyrolactone shows an absorption in its IR spectrum at 1770 cm-1 and the following 1H NMR spectral data: 2.28 (multiplet, 2 H), 2.48 (triplet, 2 H), and 4.35 (triplet, 2 H) ppm. What is the structure of y-butyrolactone?arrow_forwardtrehalose is a disacharide that can be obtained from fungi sea uchins and insects. acid hydrolysis of trehalose yields only D-glucose. trehalose is hydrolysed by a-glucosidase but not b-glucosidase.methylation of trhalose followed by hydrolysis yield two molar equivalents of 2-3-4-6 -tetra-O-methyl-D-glucopyranose. deduce the structure of the trehalose using the experimental dataarrow_forwardDraw the major product(s) for reaction of methyl pentanoate with: (2) Me2CHCH2CH2OH, H30*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