Factors Affecting Enzyme Controlled Reactions – Part 1

Here’s a reminder of the key points you need to know about four factors that affect the rate of enzyme controlled reactions. 

First, enzyme concentration affects enzyme-controlled reactions. 

Increasing enzyme concentration means increased active sites available, thus increasing the probability of enzyme-substrate complexes.

If the substrate is in excess, increasing enzyme concentration increases the rate of reaction linearly.

But, if the substrate is limiting, the rate of reaction plateaus.

Second, substrate concentration affects enzyme-controlled reactions

Increasing substrate concentration increases the probability of enzyme-substrate complexes.

If the enzyme is in excess, increasing substrate concentration increases the rate of reaction linearly. 

But, if the enzyme is limiting, the rate of reaction plateaus.

Third, inhibitors affect enzyme-controlled reactions.

Competitive inhibitors are complementary to the enzyme’s active site, lowering the probability of an enzyme-substrate complex. 

This initially decreases the rate of reaction.

Eventually, the maximum rate of reaction is still reached, since competitive inhibitors don’t permanently bind to the enzyme’s active site.

So, an increase in substrate concentration increases the probability of enzyme-substrate complexes.

At this point, another factor, such as enzyme concentration, is limiting. 

Non-competitive inhibitors don’t bind to an enzyme’s active site, but to another part of the enzyme, causing the active site to change shape.

And when the active site and substrate are no longer complementary, this prevents enzyme-substrate complexes. 

This decreases the rate of reaction, as well as the maximum rate of reaction, since increasing substrate concentration is no longer effective.