Enzyme Binding Factors - Online Tutor, Practice Problems & Exam Prep

Enzymes catalyze reactions by forming an enzyme-substrate complex (ES) at the active site, where the substrate binds specifically. 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. Cofactors enhance substrate binding, enabling the enzyme to convert substrates into products while remaining unchanged, allowing for repeated catalysis. Understanding these interactions is crucial for grasping enzyme functionality and metabolic processes.

Enzyme-Substrate Complex

In this video, we're going to begin our lesson on enzyme binding factors by introducing the enzyme substrate complex. When an enzyme interacts with its substrate, the substrate is going to bind to the enzyme specifically at a region called the active site. When the substrate binds to the enzyme at the active site, this ends up forming the enzyme substrate complex. The enzyme substrate complex is commonly abbreviated as just ES. So I'll put ES here.

The active site, once again, is defined as a very specific region of an enzyme that binds the substrates. Let's take a look at our image down below to see how substrate binding forms the enzyme substrate complex. Notice over here on the far left, we're showing the enzyme in red, and the enzyme is commonly abbreviated with just an "e". 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". Notice that when the substrate interacts with the enzyme as we indicated up above, it will bind to the enzyme specifically at the region called the active site, which is just the specific region of the enzyme that binds the substrate.

The substrate here is going to bind to the active site of the enzyme, which is just this region that we see right here. This other region over here is not the active site. The active site is this region right here. The active site is just a specific region on the enzyme that binds the substrate. Once the enzyme is bound to the substrate, it ends up forming the enzyme substrate complex.

Here in the middle, we can see the substrate is bound to the enzyme, and they are making this fit together. The enzyme substrate complex is commonly abbreviated as just ES complex. 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. Notice that after enzyme catalysis, represented by this arrow right here, the substrate 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.

This is what we mean by the enzyme being unchanged. Because the enzyme is unchanged, it means that it can continuously catalyze this reaction over and over again to continuously make more and more product over time. 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 required by an enzyme for catalysis to occur. If there is no cofactor, in some substances, 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 enzymes do. An example of cofactors includes metal ions. Some enzymes will not be able to perform catalysis without metal ions, which are non-protein because they're not made up of amino acids like proteins are; instead, they're just metal ions.

Cofactors are not consumed in the reaction, which means that at the beginning and by the end of the reaction, the cofactor remains the same. Cofactors can actually assist with enzyme catalysis in many different ways, and we'll be able to see an example of how they can assist down below in our image. A coenzyme sounds a lot like a cofactor because it is a cofactor. A coenzyme is a very specific type of cofactor, defined as an organic molecule cofactor.

If the cofactor is an organic molecule, meaning that 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; they do not contain carbon and hydrogen atoms. It's only the cofactors that are organic molecules that we call coenzymes. Coenzymes tend to be derived from vitamins.

Let's take a look at our example below to get a better understanding of how cofactors can assist enzymes with catalysis. Some cofactors can assist in substrate binding. In our image below, on the left-hand side, notice that the enzyme is shown in red and the substrate in black. Notice that the enzyme's active site here is not perfectly tailored for this substrate and perhaps the substrate in some scenarios could not bind to the active site because the active site 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 be able to bind into the active site. Once the substrate has bound into the active site, as shown on the far right, then 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 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.

Here’s what students ask on this topic:

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

The enzyme-substrate complex (ES) forms when a substrate binds to an enzyme's active site. The active site is a specific region on the enzyme tailored to fit the substrate. This binding facilitates the chemical reaction, converting the substrate into products. The enzyme remains unchanged after the reaction, allowing it to catalyze multiple reactions. This process is crucial for metabolic pathways, as it ensures efficient and repeated catalysis.

What are cofactors and why are they important for enzyme activity?

Cofactors are non-protein substances required by some enzymes for catalysis. They can be metal ions or organic molecules (coenzymes). Cofactors assist in various ways, such as enhancing substrate binding or stabilizing the enzyme-substrate complex. Without cofactors, certain enzymes cannot function, making them essential for many biochemical reactions. Coenzymes, often derived from vitamins, are a specific type of cofactor that contains carbon and hydrogen atoms.

How do cofactors assist in substrate binding?

Cofactors can modify the enzyme's active site to better fit the substrate. For example, a metal ion cofactor might bind to the active site, altering its shape to accommodate the substrate more effectively. This enhanced fit allows the substrate to bind more easily, facilitating the enzyme's catalytic activity. Without the cofactor, the substrate might not bind properly, preventing the reaction from occurring.

What is the difference between cofactors and coenzymes?

Cofactors are non-protein substances that assist enzymes in catalysis. They can be inorganic, like metal ions, or organic. 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. The key difference lies in their composition: coenzymes contain carbon and hydrogen atoms, whereas other cofactors do not.

Why do enzymes remain unchanged after catalysis?

Enzymes remain unchanged after catalysis because they act as catalysts, facilitating reactions without being consumed or altered. This allows them to repeatedly catalyze the same reaction. The enzyme's active site binds the substrate, converts it to products, and then releases the products while retaining its original structure. This property is essential for the enzyme's efficiency and the regulation of metabolic pathways.