7. Chalcone isomerase catalyzes the reaction illustrated below. A series of modification experimentswere performed on this enzyme to identify which amino acid residues might be in the active site andwhich might promote the cyclization reaction.OHHo.НоExplain the following results:A) Acetic anhydride treatment inhibited enzyme activity.B) Pyrocarbonate inhibited activity and was found to modify 7 residues. However, this enzymeonly contains 6 His and modification of these did not affect activity.C) lodoacetate inhibited activity but this effect coult be decreased in the presence of substrate orproduct.D) Methane methanethiol sulfonate modified the enzyme but did not inhibit catalytic turnover. Inaddition, this modification was reversed in the presence of B-mercaptoethanol.keNyons Rengent

Chalcone isomerase is an enzyme in Flavonoid pathway of Anthocyanine biosynthesis and catalyze the…

Answered: 7. Chalcone isomerase catalyzes the…

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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Draw me the inhibition reaction mechanism of Cysteine Protease Inhibitor (E64). How the epoxide ring is opening because of the reaction with the thiol group of cysteine and what product are being made. Please draw with arrow pushing and also explain the reason of each attack.
Which of the following statements about ribozyme catalytic residues is INCORRECT? General acid catalysis requires the standarde nucleotide exchangeable proton acidities (represented by pKa values). Ribozymes work by lowering the AG‡ through transition state stabilization without changing the overall AG of the reaction. Some ribozymes cleave phosphodiester bonds, and like proteases, can be autocatalytic. There are fewer known classes of mammalian ribozymes than mammalian enzyles.
2) A. What is meant by energetic coupling? What is meant by the term phosphorylation and what role does phosphorylation play in energetic coupling? B. Describe at least one actual example of energetic coupling.
One sample of the globular protein peroxidase is hydrolyzed by heating with 6 M HC1. A second sample is denatured by treatment with acetone. a) How does the peroxidase structure change during hydrolysis? Will this change the biological activity of peroxidase? b) How does the peroxidase structure change during denatur-ation? Will this change the biological activity of perox-idase? c) Are either of these processes likely to be reversible?
A TAMU undergraduate biochemistry student is tasked with characterizing a new enzyme. After devising an assay, the student does some initial experiments. When initiating the reaction by adding the enzyme to a solution of substrates (but no products) she finds that at the earliest times the change in the [A] is non-linear and increasing and then becomes linear for awhile and then decreases eventually to zero. Explain what is unusual and what various aspects of the time course mostly likely means.
(b) The values of kinetic parameters for a variety of synthetic ester and peptide substrates ofa- chymotrypsin are compared for the reaction scheme below where ES is the Michaelis complex, ES' E+S Substrate K₁ N-Ac-Trp–OC₂H5 N-Ac-Phe-OC2H5 N-Ac-Leu-OC2H5 N-Ac-Phe-CONH2 N-Ac-Tyr-p-nitro-anilide ES K₂ 3.5 13.0 3.2 1.7 K-₁ is the acylenzyme, P₁ is the first product to be released, P2 is the second product, k2 is the acylation rate constant, k3 is the deacylation rate constant, and kcat = k2 k3/( k2 + k³). In the table below, N- Ac = N-acetyl; -CONH₂ = carboxamide; -OC₂H5 = ethyl ester; p-nitroanilide = −NH-C6H4-NO2 simulating a peptide group. ES' K2 (S-¹) K3 (S-1) 0.84 2.2 0.19 P₁ K3 0.073 H → E+ P2 Kcat (S-1) 0.82 1.9 0.18 0.070 0.038 KM (MM) 0.08 1.3 4.2 24.0 0.35 1 Kcat/ KM (mM-¹ s¯¹) 10.3 1.5 0.04 0.003 0.11 The value of kcat for N-Ac-Phe-OC2H5 is two-fold greater than that for the L-tryptophanyl analog and more than 10-fold greater than the value of kcat for the ester substrate…
Parts of the mechanism for lysozyme are shown below. The catalytic lysozyme residue side chains can be identified as being above and below the polysaccharide chain shown at point A. Complete the missing structures (points B and E) and curly arrows (points A, B, C, D and E) in the mechanism, as well as from the knowledge you have gained, label the catalytic amino acids at point A in your mechanism with their correct name and residue number. A OH R OH O-R H₂C- HO NHAC NHAC E R D OH B R C H RO H3C- ° H₂C- NHAC Y R OH NHAC R R
3.2
Construct the mechanism of a serine-protease with a catalytic triad.
Consider the metabolic pathway show below that converts substrate A to B with the enzyme A-ase, B to C with B-ase(I), and so forth. Acety/A-ase Acetate - A-ase Deacetylase A-ase Protease & C-ase B-ase ABCD What is the mechanism of regulation of B-ase? Positive allostery Reversible Covalent modification Isoenzymes Proteolytic Activation Feedback Inhibition 1
3. The succinate dehydrogenase reaction in the direction it proceeds within the CAC is shown below (left to right): FAD FADH, H-C-H H-C-H coo- succinate dehydrogenase Succinate Fumarate AG" - O kl/mol a) Calculate the standard reduction potential for the overall reaction above. b) Based on the reduction potential, calculate and compare your standard transformed free energy change to the textbook value (above), and venture to explain any discrepancies. c) Assuming the temperature of the cell is 37 °C, calculate the equilibrium ratio of oxidized to reduced cofactor when the ratio of oxidized product to reduced substrate is 1.2. .
1. Please fully explain (use illustrate where appropriate) the Modes of Enzyme Catalysis exemplified by the serine protease: Chymotrypsin. In your answer discuss employing the illustration whenever possible: the overall reaction mechanism, stability of the reaction transition state, proximity and orientation effects, acid-base catalysis, and covalent catalysis. (c) (0) Ap Asp Toe His Asp 10 C-N bond cleavage HN Ho Ser Ger Binding of substi 196 Ser Gly alto video LBHB NH Sere HAR Proton donation by H (h) Fel of amino product yest OHN Hig Ser Ap (0) Formation of covalent (ES) Alp Me complex Serios

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