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3. Protection of Enzyme Against Denaturation by Heat When enzyme solutions are heated, there is a progressive loss of catalytic activity with time. This loss is the result of the unfolding of the native enzyme molecule to a randomly coiled conformation, because of its increased thermal energy. A solution of the enzyme hexokinase incubated at 45 °C, lost 50% of its activity in 12 mins, but when hexokinase was incubated at 45 °C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity. Explain why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.

3. Protection of Enzyme Against Denaturation by Heat When enzyme solutions are heated, there is a progressive loss of catalytic activity with time. This loss is the result of the unfolding of the native enzyme molecule to a randomly coiled conformation, because of its increased thermal energy. A solution of the enzyme hexokinase incubated at 45 °C, lost 50% of its activity in 12 mins, but when hexokinase was incubated at 45 °C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity. Explain why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.

Biochemistry
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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2. Relation between Reaction Velocity and Substrate Concentration: Michaelis-Menten Equation (a) At what substrate concentration will an enzyme having a kcat of 30 s² and a KM of 0.005 M show one-quarter of its maximum rate? (b) Determine the fraction of Vmax that would be found in each case when [S] = ½KM, 2KM, and 10KM. 3. Protection of Enzyme Against Denaturation by Heat When enzyme solutíons are heated, there is a progressive loss of catalytic activity with time. This loss is the result of the unfolding of the native enzyme molecule to a randomly coiled conformation, because of its increased thermal energy. ´A solution of the enzyme hexokinase incubated at 45 °C, lost 50% of its activity in 12 mins, but when hexokinase was incubated at 45 °C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity. Explain why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.
Transcribed Image Text:2. Relation between Reaction Velocity and Substrate Concentration: Michaelis-Menten Equation (a) At what substrate concentration will an enzyme having a kcat of 30 s² and a KM of 0.005 M show one-quarter of its maximum rate? (b) Determine the fraction of Vmax that would be found in each case when [S] = ½KM, 2KM, and 10KM. 3. Protection of Enzyme Against Denaturation by Heat When enzyme solutíons are heated, there is a progressive loss of catalytic activity with time. This loss is the result of the unfolding of the native enzyme molecule to a randomly coiled conformation, because of its increased thermal energy. ´A solution of the enzyme hexokinase incubated at 45 °C, lost 50% of its activity in 12 mins, but when hexokinase was incubated at 45 °C in the presence of a very large concentration of one of its substrates, it lost only 3% of its activity. Explain why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.
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