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 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_forwardProve that gentiobiose forms osazone and can undergo mutarotation can be hyrolyzed by Emulsin β-glycosidase forms these hydrolysis products following permethylation: 2,3,4,6-tetra-O-methyl-D-glucose and 2,3,4-tri-O-methyl-D-glucosearrow_forwardCarbonic anhydrase facilitates the dissolution of carbon dioxide gas into water by catalyzing its hydration. Is the catalyzed reaction efficient? By what criterion do you state that?arrow_forward
- Imidazoleglycerol‑phosphate dehydratase is an enzyme in the histine biosynthesis pathway. It catalyzes the E1 dehydration of D‑erthyro‑imidazole‑glycerol phosphate to imidazole acetol‑phosphate. This is a rare example of a biological E1 reaction, as most biological elimination reactions occur through E1cB instead. In this reaction, D‑erthyro‑imidazole‑glycerol phosphate is first protonated to form a good leaving group. Then, the leaving group is ejected to form the resonance‑stabilized carbocation shown. Draw curved arrows forming the most stable resonance structure to explain why this reaction goes through an E1 mechanism. Draw curved arrows to form the most stable resonance structure.arrow_forwarda) The D-aldopentose A, C5H1005, reacts with HNO3 to yield an optically active aldaric acid B. Kiliani-Fischer chain extension of A produces a pair of D-aldohexoses C and D. C is converted by HNO3 to an optically active aldaric acid, but D is converted by HNO3 to an optically inactive aldaric acid. Write acyclic Fischer projections for A, B, C, D. b) Disaccharide E is a reducing sugar. It is hydrolyzed by an α-glycosidase enzyme, which means it contains an α- glycoside link. Treatment of E with Ag2O and excess Mel gives an octamethyl derivative F. Hydrolysis of F in dilute aqueous acid gives the pair of molecules shown below. Write the structures of E and F. (If the stereochemistry at a particular carbon is not determined by the above data, indicate this with a wavy line as shown below.) HO OMe OMe MeO MeO MOH OMe mOH OMe OMearrow_forwarda) The D-aldopentose A, C5H1005, reacts with HNO3 to yield an optically active aldaric acid B. Kiliani-Fischer chain extension of A produces a pair of D-aldohexoses C and D. C is converted by HNO3 to an optically active aldaric acid, but D is converted by HNO3 to an optically inactive aldaric acid. Write acyclic Fischer projections for A, B, C, D.arrow_forward
- d-Glucuronic acid is found widely in plants and animals. One of its functions is to detoxify poisonous HO-containing compounds by reacting with them in the liver to form glucuronides. Glucuronides are water soluble and, therefore, readily excreted. After ingestion of a poison such as turpentine or phenol, the glucuronides of these compounds are found in urine. Draw the structure of the glucuronide formed by the reaction of beta-d-glucuronic acid and phenol.arrow_forwardPyruvate carboxylase is thought to activate CO2 by ATP, through formation of carboxyphosphate as an intermediate. Propose a mechanism for the formation of this intermediate.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
- The first step in the catabolism of most amino acids is the removal of the nitrogen atom by transfer to an a-keto acid, a reaction catalyzed by an enzyme called a transaminase. The a-keto acid acceptor is often a-ketoglutarate. Modify the structures in the product to show the products of the transamination of cysteine. Be sure to show functional groups with the charge and number of attached hydrogen atoms appropriate for pH 7.4. transaminase + O=C H₂N-CH + CH₂ CH₂ CH₂ SH Incorrect H₂N || CH | CH₂ | CH₂ I || O || n | CH₂ T SHarrow_forwardKojibiose is a reducing sugar that forms D-glucose on hydrolysis with aqueous acid. Reaction of kojibiose with iodomethane and Ag20 yields an octamethyl derivative, which can be hydrolyzed with aqueous acid to give one equivalent of 2,3,4,6-tetra-O- methyl-D-glucopyranose and one equivalent of 3,4,6-tri-O-methyl-D-glucopyranose. If kojibiose is hydrolyzed by alpha-glucosidases but not beta-glucosidases, what is its structure?arrow_forwardWhich of the following functional group (FG) will produce a ketone upon oxidation with K2CrO7? (a) RX (b) 10OH (b) 20OH (c) 30OHarrow_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