Answer to Question #335827 in Biochemistry for Anthony

Question

Discuss the different mechanisms by which enzyme activity can be regulated in a cell, also

explain why regulation of enzyme activity is crucial to sustain cellular life.

Answer 1

The cells of your body are capable of making many different enzymes, and at first you might think: great, let’s crank all of those enzymes up and metabolize as fast as possible! As it turns out, though, you really don’t want to produce and activate all of those enzymes at the same time, or in the same cell.

Needs and conditions vary from cell to cell and change in individual cells over time. For instance, stomach cells need different enzymes than fat storage cells, skin cells, blood cells, or nerve cells. Also, a digestive cell works much harder to process and break down nutrients during the time that follows a meal as compared with many hours after a meal. As these cellular demands and conditions changes, so do the amounts and functionality of different enzymes.

Because enzymes guide and regulate the metabolism of a cell, they tend to be carefully controlled. In this article, we’ll take a look at factors that can affect or control enzyme activity. These include pH and temperature (discussed in the active site article), as well as:

• Regulatory molecules. Enzyme activity may be turned "up" or "down" by activator and inhibitor molecules that bind specifically to the enzyme.
  
• Cofactors. Many enzymes are only active when bound to non-protein helper molecules known as cofactors.
  
• Compartmentalization. Storing enzymes in specific compartments can keep them from doing damage or provide the right conditions for activity.
  
• Feedback inhibition. Key metabolic enzymes are often inhibited by the end product of the pathway they control (feedback inhibition).

In the rest of this article, we'll examine these factors one at a time, seeing how each can affect enzyme activity.

Regulatory molecules

Enzymes can be regulated by other molecules that either increase or reduce their activity. Molecules that increase the activity of an enzyme are called activators, while molecules that decrease the activity of an enzyme are called inhibitors.

There are many kinds of molecules that block or promote enzyme function, and that affect enzyme function by different routes.