Alright. So now that we've covered the first three major classes of enzymes, oxidoreductases, transferases, and hydrolases, we can move on to our 4th major class of enzyme, which in our mnemonic Over the Hill is the I. And of course, the I stands for isomerases. And isomerases are enzymes that pretty much do exactly what they sound like, which is catalyzing the creation of an isomer. And of course, they do that by shifting functional groups around to different locations within the same exact molecule. And so recall from our previous lessons that isomers are just molecules that have the same exact chemical formula with just a different arrangement of atoms. And so a classic example of an isomerase is the enzyme triose phosphate isomerase, which produces an isomer during glycolysis. And later in our course when we cover glycolysis in more detail, we'll revisit this triose phosphate isomerase enzyme.

Now, below in our example, we're showing the reaction that triose phosphate isomerase catalyzes, and it catalyzes the conversion of dihydroxyacetone phosphate, or DHAP, into glyceraldehyde 3-phosphate, or G3P. Essentially, what you'll notice is the only difference between DHAP and G3P is the arrangement of the atoms because they have the same exact chemical formula, and therefore, they are isomers of one another. Dihydroxyacetone has the hydroxyl group on the end, and it has a carbonyl group in the middle, whereas glyceraldehyde 3-phosphate has the carbonyl group on the end and the hydroxyl group in the middle. And so again, because there is this creation of an isomer, that classifies triose phosphate isomerase as an isomerase. And so again, we'll be able to get a little bit of practice in our next practice video, so I'll see you guys there.