. The allosterically regulated enzyme ATCase binds aspartic acid as asubstrate and acylates the a-amino group. Succinate acts as a competitiveinhibitor of ATCase because it binds the active site but can't be acylated. Thedependence of vo on [aspartic acid] for ATCase is shown in panel (a) of theaccompanying figure. Panel (b) shows the effect of increasing [succinate]on v, when [Asp] is held at a low concentration (see thick vertical arrow inpanel (a)). Note that in panel (b), vo is not zero when [succinate] =0 (seethin horizontal arrow). Explain the shape of the curve in panel (b). Whydoes v, increase initially, before decreasing at higher [succinate]?Co0-COOCH2CH,HC -NH,CH,COOCOOAspSuccinate[Asp)[Succinate][Asp] inexperiment b(a)(b)

The allosterically regulated enzyme ATCase binds aspartic acid as a substrate and acylates the…

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Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter10: From Proteins To Phenotypes

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

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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]?
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.
Serine Proteases, such as chymotrypsin, contain Ser/Asp/His as a catalytic triad (i.e. three collaborating amino acids) of amino acids involved in enzyme catalysis. Why is this? Examine each amino acid of this catalytic triad (schematically detailed below: Ser195/Asp102/His57) and, based on your understanding of amino acid characteristics, predict what the role of each amino acid could be. His57 Ser195 Asp102
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.
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.
In 1966, Ferdinand showed that a random-order ternary-complex mechanism for a two-substrate enzyme-catalysed reaction can lead to sigmoidal kinetics being observation in the absence of cooperative binding. Discuss this scenario so that it is clear why a plot of Vo versus [AXo] at constant [Bo] will be sigmoidal.
The inilial reactions in the biosynthesis of the amino acid aspartate at 298 K are: Carbamoyphoephate Cartamoyi + phosphate ADP + phoaphate - ATP AO=-12,300 calmol AG-T800 calimol Which of the following statements is gorrect? A) The energy which is released fron the conversion of 1 mole of carbamoyphosphate to carbamoyl+ phosphate (P) in reaction I is sufficient to drive the synthesis of 1 mole of ATP in reaction II. B) AG for the reaction Carbamoyphosphate + Carbamoyl + phosphate is +123 kcalimol. c) AHP for reaction I cannot be detemined trom the information given. D) Al of the above. E) None of the above.
PLP is a cofactor for a number of enzymes involved in amino acid metabolism. Give an example of reaction in which PLP participates in cleavage of the a, b, and c bonds of an amino acid, as diagrammed in shown Fig.
Neuraminidase (NA) catalyzes a hydrolysis of the glycosidic linkages of sialic acids using a mechanism shown in Fig. (a). and Fig. (b) shows competitive inhibitors of NA Considering the mechanism of NA, why do zanamivir and oseltamivir inhibit NA so potently?
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
Fructose 1,6-bisphosphatase (FBPase) is a key enzyme in gluconeogenesis. The mammalian enzyme is tetrameric, negatively regulated by both Fructose 2,6-bisphosphate and AMP. Propose three (3) distinct models for how these molecules regulate FBPase activity. Also, describe how the enzyme might differentiate between Fructose 1,6 bisphosphate and Fructose 2,6-bisphosphate binding to the allosteric site on the enzyme with particular emphasis on amino acids comprising the allosteric binding site(s).
Which one of the following would best allow us to conclude that the rate of chymotrypsin was pseudo-first-order with respect to the peptide Leu-Phe- Gly, based on our coverage? O None of the other options are suitable because this enzyme catalyzes a reaction with only one substrate. O If the reaction is of the ordered sequential type, with the peptide binding second. O If the concentration of peptide is quite low. O If the peptide concentration is much higher than the Km. O If the reaction is of the ordered sequential type, with the peptide binding first.

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