Gerhart and Pardee measured ATCase activity in the presence of a variety of purine and pyrimidinederivatives. Their results are presented in Table 2. What compound(s) were the most effectiveinhibitors? activators? Explain the significance of the metabolites that served as inhibitors oractivators in the context of the biosynthetic pathway presented in Figure 1.Table 2: Effect of nitrogen bases, nucleosides and nucleotides on ATCase activity. *Indicatesstimulation. (Based on Gerhart and Pardee, 1962.)Compound Inhibition, % (Conc = 2 mm)Cytosine0Cytidine24CMP38dCMP48CTP86dCTP88UTP8GTP35dGTP31-180*-162*ATPdATP

Aspartate Transcarbamylase is an enzyme which regulate early step in synthesis of pyramidine…

Answered: Gerhart and Pardee measured ATCase…

Biochemistry

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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What is the catalytic triad on chymotrypsin? Detail its importance.
the structures of chymotrypsin and other serine proteases revealed that the active sites of these enzymes shared a particular sterochemical arrangement of residues crucial to their activity. This came to be known as the catalytic triad, as it consisted of the oponyomous serine (Ser) residue, along with a histidine (His) and an aspartate (Asp) residue. Which of the following would result in the greatest decrease in function of the catalytic triad found in serine proteases? O Mutation to Ser, Cys, Asp O Mutation to Ser, His, Asp O Mutation to Cys, His, Asp O Mutation to Ser, His, Glu
Answer the question below
The initial velocities of two different enzyme-catalyzed reactions were measured over a series of substrate concentrations. The following results were obtained: Enyme A: KM = 1.5 mM, Vmax = 10 μM s-1 Enyme B: KM = 5.0 mM, Vmax = 85 µM s-1 (a) Which enzyme binds to its substrate more tightly (assume k.1 >> k₂ in the Michaelis-Menten model)? (b) Calculate the initial velocities of each reaction when the substrate concentration is 2.5 mM. (c) Calculate the Kcat of each enzyme if the total enzyme concentration is 100 nM. (d) Which enzyme is the more efficient catalyst? Explain your answer. The enzyme carbonic anhydrase is strongly inhibited by the drug acetazolamide. A plot of the initial reaction velocity (as a percentage of Vmax) in the absence and presence of the inhibitor is shown below. What type of inhibition is taking place? Explain your reasoning. V (% of Vmax) 100 50 0.2 0.4 No inhibitor Acetazolamide [S] (MM) 0.6 0.8 1
Draw a schematic illustration of the hydrolysis of N-acetylphenylalaninamide catalyzed byalpha-chymotrypsin in which you indicate the important catalytic residues in the active site and how thesubstrate undergoes transformation to products through two different tetrahedral intermediates.
Considering that triacylglycerols get hydrolyzed in the small intestine because of pancreatic lipases, write the reactions using structural formulas by which a 7-carbon fatty acid is activated and oxidized in the liver of this patient. Indicate cofactors and underscore the final CoA products.
The enzymatic activity of PFK1 is generally measured by set- ting up a coupled enzyme assay system whereby aldolase, triose phos- phate isomerase, and glycerol-3-phosphate dehydrogenase are added to the assay mixture. For the latter enzyme, NADH is added and its change in concentration is readily monitored at 340 nm. Write the chain of reactions catalyzed by these enzymes using structural formulas, label substrates and products, and explain why the coupled en- zyme assay system leads to oxidation of NADH. While the chain of reac- tions is similar to those in glycolysis, there is a critical difference because of the dehydrogenase enzyme. Describe how this enzyme causes the chain of reactions to differ from those in glycolysis.
Why is de novo biosynthesis of purines markedly elevated in patients with a deficiency in hypoxanthine-guanine phosphoribosyl transferase (HGPRT)? 5-Fluoruracil is converted to methotrexate by a DPD deficiency, leading to increased purine biosynthesis. HGPRT deficiency prevents purine salvage, leading to increased purine biosynthesis to make up for it. HGPRT increases pyrimidine salvage and thereby increases purine biosynthesis as a result. Increased purine biosynthesis is the result of ATP hydrolysis during the production of cyclic AMP.
Briefly explain how ester hydrolysis experiments helped to provide evidence for the mechanism of peptide hydrolysis catalyzed by chymotrypsin.
Since all of the ββ-lactams that you have tested are susceptible to hydrolysis by PaESBL-1, the hospital will not be able to use a single ββ-lactam to combat this P. aeruginosa isolate. You need to consider alternative strategies. From the following list, select all of the strategies that might successfully overcome the broad substrate specificity of PaESBL-1:
Put these steps in the mechanism of chymotrypsin catalysis in order from first to last. Note that some references may not break out each of these steps individually, but all steps should be ordered. There will be eight steps.
Answer the following questions about the inhibition of acetylcholine esterase by neostigmine. 5a. Does neostigmine have a structure that enables it to bind reversibly to the ACbE active site? 5b. Is neostigmine catalytically processed by ACHE? 5c. How does the stability of the carbamolyl-enzyme intermediate produced by treatment of ACbE with neostigmine compare to the stability of the acetyl- enzyme intermediate produce when ACb, is hydrolyzed?

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