n a particular enzyme, an alanine residue is located in a cleft where the substrate binds. A mutation that changes this residue to glycine has little effect on activity; however, another mutation, which changes the alanine to a glutamate residue, leads to a complete loss of activity. Provide a brief explanation for these observation

n a particular enzyme, an alanine residue is located in a cleft where the substrate binds. A mutation that changes this residue to glycine has little effect on activity; however, another mutation, which changes the alanine to a glutamate residue, leads to a complete loss of activity. Provide a brief explanation for these observation

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter10: From Proteins To Phenotypes

Section: Chapter Questions

Problem 14QP: If phenylalanine was not an essential amino acid, would diet therapy (the elimination of...

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In a particular enzyme,an alanine residue is located in a cleft where the substrate bonds.A mutation that changes this residue to glycine has little effect on activity,however another mutation ,which changes the alanine to a glutamate residue,leads to loss of activity.Provide a brief explanation for those observation
Snake venom contains many hydrolase enzymes, including several serine proteases. One such protease (present in high concentrations in snake venom) mimics the action of thrombin to activate fibrin. The venom protease cleaves peptide bonds with a specificity for basic, positively charged amino acids. This enzyme is incubated with a substrate peptide with the sequence SNPDCKVALYMTW. Draw a mechanism for the peptide hydrolysis of this specific peptide catalyzed by this snake venom protease. Include the structure of the active site amino acids of the enzyme and the substrate peptide group (including the full structure of the 2 specific amino acids that contribute to the scissile peptide group in the substrate) in your mechanism. Use the curved arrow convention to illustrate the flow of electrons.
Phosphonacetyl-L-aspartate (PALA) is a potent inhibitor of aspartate transcarbamoylase because itmimics the two physiological substrates of the enzyme. However, in the presence of substrates, lowconcentrations of PALA increase the reaction rate of aspartate transcarbamoylase. Explain this result.
A carboxypeptidase is a metalloenyme (its active site contains one or more metal ions essential for the function) that catalyzes the hydrolysis of the peptide bond of the terminal amino acid of a polypeptide chain (where the free carboxyl group occurs). The binding of an L-alanyl-L-tyrosine peptide substrate in the active site of the enzyme is represented in the scheme below: Glu Zn++ COO™ OH H3C CH₂ HC NH IO C H H Poche apolaire -H H O+N: C N H H H NH₂ Arg 145 Туг 248 NB: This scheme gives a planar representation of the spatial structure of the active site where indicated contacts (hatched lines) are supposed to occur in the 3D structure of the enzyme. 1- Describe the interactions that occur between the ligand and amino acid residues of the active site. 2- What would be the impact on the Km value if we replace L-alanyl-L-tyrosine by the following substrates: L-alanyl-L-phenylalanine; L-alanyl-L-aspartate; L-aspartyl-L- tyrosine.
You have isolated a new protease that cleaves peptide bonds on the carboxyl side of Asp and Glu. Based on the enzyme's inactivation by DIPF, you suspect that it may utilize a mechanism similar to chymotrypsin. The difference in specificity might be explained by the absence of the S1 binding pocket. replacement of serine 195 with a positively charged residue. presence of a positively charged residue in the S1 binding pocket. presence of a negatively charged residue in the S1 binding pocket.
The allosterically regulated enzyme ATCase binds aspartic acid as a substrate and acylates the α–amino group. Succinate acts as a competitiveinhibitor of ATCase because it binds the active site but can’t be acylated.The dependence of v0 on [aspartic acid] for ATCase is shown in panel (a)of the accompanying figure. Panel (b) shows the effect of increasing [succinate] on v0 when [Asp] is held at a low concentration (see thick vertical arrow in panel (a)). Note that in panel (b), v0 is not zero when [succinate] = 0 (see thin horizontal arrow). Explain the shape of the curve in panel (b). Why does v0 increase initially, before decreasing at higher [succinate]?
The enzyme mutase which is important for the synthetic of tyrosine and phenylalanine in saccharomyces cerevisiae has been studied as an example of an allosteric enzyme. Tyrosine acts as a negative effector for this enzyme. What effects would you see on the action of the enzyme were you to increase the concentration of tyrosine? The chorismate mutase would shift to its R conformation The curve showing the kinetics or chorismate mutase would shift to the right The curve showing the kinetics of chorismate mutase would shift to the left The chorismate mutase would become saturated more rapidly
Diisopropylphosphofluoridate (DIPF) inactivates chymotrypsin by covalently modifying serine 195. Which statement is true of DIPF's inhibitory mechanism? DIPF randomly modifies all serine residues on the protein, and if enough is added, the serine in the active site will eventually be modified. DIPF approaches serine 195 more closely than other substrates. DIPF looks like the substrate for chymotrypsin and binds in the active site as a competitive inhibitor. Serine 195 is in an environment that gives it a higher than normal reactivity with respect to DIPF.
Because it resembles the two physiological substrates, phosphonacetyl L - aspartate (PALA) is a strong inhibitor of ATCase. Low concentrations of this unreactive bisubstrate analog, on the other hand, enhance reaction velocity in the presence of substrates. The reaction rate rises as PALA is added, until three molecules of PALA are attached per molecule of enzyme. This maximum velocity is 17 times higher than it would be without PALA. With the addition of three additional molecules of PALA per molecule of enzyme, the reaction rate drops to practically nil. Why does PALA activate ATCase at such low concentrations?
The enzyme aspartate transcarbamoylase catalyzes an early step in pyrimidine biosynthesis. The two states of the multi-subunit enzyme are shown below. Note that the binding of the regulatory molecule CTP (cytosine triphosphate) causes the enzyme complex to be inactive. Is this situation an example of positive or negative regulation? Explain why the use of CTP as the regulatory molecule is logical givén the overall function of this particular enzyme. INACTIVE ENZYME: T STATE catalytic subunits regulatory subunits OFF 6 CTP ON ACTIVE ENZYME: R STATE
An example of an enzyme-catalyzed reaction proceeding via a transition-state stabilization mechanism is the hydrolysis of peptides by chymotrypsin while, Lysozyme is often cited as an example of an enzyme which operates by strain mechanism. Discuss both mechanisms in the context of each enzyme.
b) Following this experiment, you would like to elucidate the mechanism of action of pyruvate kinase. Unfortunately, the crystal structure of pyruvate kinase is not available, which requires the enzyme to be modelled based on the available three-dimensional structures of related enzymes. Suggest a bioinformatics approach that can be conducted to perform this study.