Which of the following characteristics is most likely to be associated with an enzyme that catalyzes two different chemical reactions?
A) The enzyme contains α-helices and β-pleated sheets.
B) The enzyme is subject to competitive inhibition and allosteric regulation.
C) The enzyme is composed of at least two subunits.
D) Either the enzyme has two distinct active sites or the substrates involved in the two reactions have very similar structures.

Question

Quizplus · Accepted Answer

If an enzyme catalyzes two different chemical reactions, it must have two distinct active sites for each reaction or the substrates involved in the two reactions must have very similar structures that can bind to the same active site. Therefore, choice D is the correct answer. The other choices are not necessarily associated with enzymes that catalyze two different reactions. For example, while many enzymes contain α-helices and β-pleated sheets (choice A), this characteristic is not specific to enzymes that catalyze two different reactions. Similarly, while enzymes can be subject to both competitive inhibition and allosteric regulation (choice B) or composed of two or more subunits (choice C), these characteristics are not inherently linked to catalysis of two different reactions.

Which of the Following Characteristics Is Most Likely to Be