Lysine catabolism begins with reductive amination of a-ketoglutarate to give saccharopine in a multistep process.Draw curved arrows to show the movement of electrons in this step of the reaction mechanism.Arrow-pushing Instructions7COOH NH3COOOOCB:COOH NH3COOBH+

Answered: Lysine catabolism begins with reductive…

Organic Chemistry

9th Edition

ISBN:9781305080485

Author:John E. McMurry

Publisher:John E. McMurry

Chapter29: The Organic Chemistry Of Metabolic Pathways

Section29.SE: Something Extra

Problem 53AP

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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.
The phosphoryl group on phosphoglucomutase is slowly lost by hydrolysis. Propose a mechanism that utilizes a known catalytic intermediate for restoring this essential phosphoryl group. How might this phosphoryl donor be formed?
Pyruvate carboxylase is thought to activate CO2 by ATP, through formation of carboxyphosphate as an intermediate. Propose a mechanism for the formation of this intermediate.
Acetolactate synthase is another TPP-requiring enzyme. It transfers the acyl group of pyruvate to another molecule of pyruvate, forming acetolactate. This is the first step in the biosynthesis of the amino acids valine and leucine. Propose a mechanism for this reaction.
List the following in order of increasing tendency to accept electrons: (a) α-ketoglutarate + CO2 (yielding isocitrate); (b) oxaloacetate; (c) O2; (d) NADP+.
The vitamin Niacin is used to form nicotinamide adenosine dinucleotide, which readily shuttles between its oxidized (NAD+) and reduced (NADH) forms. The latter serves as a cellular equivalent to NaBH4. The essential portions of the structures are shown below. Outline a mechanism for the cellular conversion of pyruvate to lactate. (Note: like NaBH4, NADH cannot reduce carboxylic acid carbonyls).
The same E1–E2–E3 multienzyme structure found in the pyruvate dehydrogenase and the a-ketoglutarate dehydrogenase complexes is also used in the branched-chain a-ketoacid dehydrogenase complex, which participates in the catabolism of branched-chain amino acids. Draw the reaction product when the following substrate is acted on by the branched-chain a-keto acid dehydrogenase complex.
The given mechanism of transamination reaction is shown below, To complete the shuffling of amino groups and carbonyls, the PMP must be converted back to PLP. How would you predict that this occurs? 1. A separate reaction oxidizes the amine group of PMP to an aldehyde. 2. A separate reaction hydrolyzes the amine of PMP to an aldehyde. 3. A different ketoacid reacts with the amine of PMP, and the entire sequence runs backward. 4. Either 2 or 3 could occur.
The final step in the metabolic degradation of uracil is the oxidation of malonic semialdehyde to give malonyl CoA. Propose a mechanism.
Assume that acetyl CoA containing a 14C isotopic label in the carboxyl carbon atom is used as starting material for the biosynthesis of mevalonate, as shown in Figure 27-7. At what positions in mevalonate would the isotopic label appear?
Match the following general enzyme names and reactions catalyzed: Enzyme Reaction catalyzed a. decarboxylase b. phosphatase c. peptidase d. esterase formation of ester linkages removal of carboxyl groups from compounds hydrolysis of peptide linkages hydrolysis of phosphate ester linkages
The given mechanism of transamination reaction is shown below, What is the role of the pyridinium group in Step D? 1. It acts as an electron-donating group (source) of electrons to enhance deprotonation of the amino acid by the enzyme. 2. It acts as an electron-withdrawing group (sink) to facilitate deprotonation of the amino acid. 3. It plays the role of a Lewis base to coordinate the amino acid. 4. Both 2 and 3 are true.

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Lysine catabolism begins with reductive amination of a-ketoglutarate to give saccharopine in a multistep process. Draw curved arrows to show the movement of electrons in this step of the reaction mechanism. Arrow-pushing Instructions 7 COO H NH3 COO OOC B: COO H NH3 COO BH+