Enzyme Binding Factors: Videos & Practice Problems

Enzymes interact with substrates at a specific region called the active site, forming the enzyme-substrate complex (ES). This complex facilitates catalysis, allowing substrates to be converted into products while the enzyme remains unchanged, enabling repeated reactions. Some enzymes require cofactors, non-protein substances that assist in catalysis, such as metal ions. Coenzymes, a type of cofactor, are organic molecules derived from vitamins. They enhance substrate binding, ensuring effective enzyme activity and promoting efficient biochemical reactions.

Enzyme-Substrate Complex

In this video, we're going to begin our lesson on enzyme binding factors by introducing the enzyme-substrate complex. And so when an enzyme interacts with its substrate, the substrate is going to bind to the enzyme specifically at a region called the active site. And so when the substrate binds to the enzyme at the active site, this ends up forming the enzyme-substrate complex. And the enzyme-substrate complex is commonly abbreviated as just ES. So I'll put ES here. And so the active site, once again, is defined as a very specific region of an enzyme that binds the substrates.

So let's take a look at our image down below to look at how substrate binding forms the enzyme-substrate complex. And so notice over here on the far left, we're showing the enzyme over here in red, and the enzyme is commonly abbreviated with just an e. And then notice that in black right here, we're showing you the substrate which is really acting as the reactant for this enzyme-catalyzed reaction, And substrates are commonly abbreviated with just the letter s. And so notice that when the substrate active site. And the active site is just the specific region of the enzyme that binds the substrate. And so the substrate here is going to bind to the active site of the enzyme, which the active site of the enzyme is just this region that we see right here. And so, this other region over here is not going to be the active site. The active site is this region right here. So the active site is just a specific region on the enzyme that binds the substrate.

And so once the enzyme is bound to the substrate, it ends up forming the enzyme-substrate complex. And so here in the middle, we can see the substrate is bound to the enzyme, and they are making this fit together. And so, the enzyme-substrate complex is commonly abbreviated as just ES complex. Now after enzyme catalysis, it's the products that are going to be released from the active site, and the enzyme is going to remain unchanged in the reaction. And so notice that after enzyme catalysis, which would be represented by this arrow right here, the substrate in in black is being converted into the product over here, which is in green, and the products are commonly abbreviated with just a p. But notice that the enzyme is actually unaltered, it is unchanged by the end of the reaction. And so the enzyme still takes on the original form that it had before the reaction even took place. And so this is what we mean by the enzyme being unchanged. And because the enzyme is unchanged, it means that it can continuously catalyze this reaction over and over and over again to continuously make more and more product over time. And so this here concludes our introduction to the enzyme-substrate complex.

As we move forward, we'll be able to talk about some more enzyme binding factors. So I'll see you all in our next video.

Cofactors

In this video, we're going to introduce cofactors. Some enzymes require what are known as cofactors, which are defined as non-protein substances that are required by an enzyme for catalysis to occur. If there is no cofactor, in some cases, no enzyme catalysis can take place. You can think of cofactors as basically little enzyme helpers. They help the enzyme perform enzyme catalysis. Not all enzymes have cofactors, but some do. An example of cofactors includes metal ions. Some enzymes will not be able to perform catalysis without metal ions. Metal ions are non-protein because they are not made up of amino acids like proteins; instead, they are just metal ions. Cofactors are not consumed in the reaction, which means that at the beginning of the reaction and by the end of the reaction, the cofactor remains the same. Cofactors can assist with enzyme catalysis in many different ways, and we'll see an example of how they can assist down below in our image.

A coenzyme sounds a lot like a cofactor, and that's because it is a cofactor. A coenzyme is a very specific type of cofactor defined as an organic molecule. If the cofactor is an organic molecule, meaning it contains carbon and hydrogen atoms, then we refer to it as a coenzyme. Not all cofactors are coenzymes because not all cofactors are organic molecules. For example, metal ions are just made up of metal atoms, not containing carbon and hydrogen atoms. Thus, only the cofactors that are organic molecules are called coenzymes. Coenzymes tend to be derived from vitamins.

Let's take a look at our example down below to get a better understanding of how cofactors can assist enzymes with catalysis. Some cofactors can assist in substrate binding. Notice that the enzyme is shown in red and the substrate in black. However, the enzyme's active site here is not really tailored for this substrate; perhaps the substrate could not bind to the active site because it is not perfectly tailored for the substrate. If that happens, then the enzyme will not be able to perform catalysis. However, if a cofactor is present, such as this orange structure representing the cofactor, then the cofactor can bind into the active site. Notice here the cofactor is bound to the active site, which could make the active site better suited and better tailored for the substrate. Only in the presence of the cofactor will the substrate actually be able to bind into the active site. Once the substrate has bound into the active site, as shown on the far right, enzyme catalysis can proceed, and the enzyme can convert the substrate into the product, which is not shown here, but you can imagine the reaction continuing as normal.

This concludes our introduction to cofactors and how they are non-protein substances that are required to help enzymes perform catalysis. We'll be able to get some practice applying these concepts as we move forward in our course, so I'll see you all in our next video.

The organic non-protein components that aid in enzyme catalysis are called:
a) Reactants.
b) Cofactors.
c) Coenzymes.
d) Substrates.
e) Products.

• A. Reactants.
• B. Cofactors.
• C. Coenzymes.
• D. Substrates.
• E. Products.

Answer: (C)

Here’s what students ask on this topic:

What is the enzyme-substrate complex and how does it facilitate catalysis?

The enzyme-substrate complex (ES) forms when a substrate binds to an enzyme's active site. This specific region on the enzyme is tailored to fit the substrate, allowing the enzyme to catalyze the reaction. Once the substrate is bound, the enzyme facilitates its conversion into products. Importantly, the enzyme remains unchanged after the reaction, enabling it to catalyze multiple reactions repeatedly. This process ensures efficient biochemical reactions, as the enzyme can continuously convert substrates into products without being consumed.

What are cofactors and how do they assist in enzyme catalysis?

Cofactors are non-protein substances required by some enzymes for catalysis. They can be metal ions or organic molecules (coenzymes). Cofactors assist enzymes in various ways, such as enhancing substrate binding. For instance, a cofactor can bind to the enzyme's active site, making it better suited for the substrate. This ensures that the substrate can bind effectively, allowing the enzyme to perform catalysis. Cofactors are not consumed in the reaction, meaning they remain unchanged and can assist in multiple catalytic cycles.

What is the difference between cofactors and coenzymes?

Cofactors are non-protein substances that assist enzymes in catalysis. They can be either inorganic, like metal ions, or organic molecules. Coenzymes are a specific type of cofactor that are organic molecules, typically derived from vitamins. While all coenzymes are cofactors, not all cofactors are coenzymes. Coenzymes contain carbon and hydrogen atoms, whereas inorganic cofactors, like metal ions, do not. Both types of cofactors enhance enzyme activity, but their chemical nature distinguishes them.

How do enzymes remain unchanged after catalysis?

Enzymes remain unchanged after catalysis because they act as catalysts, facilitating the conversion of substrates into products without being consumed in the process. During the reaction, the enzyme forms a temporary enzyme-substrate complex, but once the reaction is complete, the products are released, and the enzyme returns to its original state. This allows the enzyme to participate in multiple catalytic cycles, continuously converting substrates into products without undergoing any permanent changes.

Why are some enzymes unable to perform catalysis without cofactors?

Some enzymes require cofactors because their active sites alone are not sufficient to bind substrates effectively or to catalyze the reaction. Cofactors can modify the enzyme's active site, making it more suitable for substrate binding. Without these cofactors, the enzyme may not achieve the proper conformation needed for catalysis, rendering it inactive. Cofactors essentially act as helpers, ensuring that the enzyme can perform its catalytic function efficiently.