Chapter 6, Problem 1Q

Summary Introduction

To review:

The features of an enzyme structure that makes it specific for a specific substrate.

Introduction:

Enzymes are chemically proteins in their folded tertiary structure and contain specific active sites. Hexokinase belongs to a class of enzyme that catalyzes the adenosine triphosphate(ATP)dependent phosphorylation of certain hexoses (six carbon sugars). They only bind to sugar thatis in D-form. The interaction between enzyme and substrate is highly specific.

Explanation of Solution

Every enzyme has an active site, which is specific for a specific substrate. This can be illustrated by the lock and key model. A particular key can open a particular lock, likewise a particular enzyme can catalyze a particular substrate. This is the most important feature of enzyme specificity. Incase of hexokinase, they have an active site that is specific for only D-form of hexose sugars. Both substrate and enzyme have complementary structures, which facilitate their interaction.

Specificity of the enzyme depends upon the interaction of active site amino acids with the substrate. Some enzymes requirenonprotein components called cofactors for their activity. The cofactors may be ions, such as ${\text{Mg}}^{\text{2+}}$ or ${\text{Zn}}^{\text{2+}}$. Thesemay also be complex organic molecules called coenzymes. Cofactors and coenzymes also enhance the functioning of specific enzymes by making the active site more favorable for binding of substrates.

Conclusion

Thus, it can be concluded that the enzyme has an active sit, ehich has the structure complementary to the specific substrate. This is like a lock and key. There are cofactors and coenzymes that are also responsible for the specificity of the enzyme.