 enzymes, also called the bio catalyst that speeds up the rate of reactions, chemical reactions inside your body. Now you must have learnt a lot about enzymes, about its structure, how it functions, how it increases the rate of chemical reactions. But in this video, we are going to learn about enzyme names. So before we proceed, I want you to pause the video and write few enzyme names on a paper, at least two or three of them. Alright, now I want you to carefully look at the words that you wrote. Do you see an ASE suffix at the end of each word you wrote? Let me write a few examples for you, lactase, urease, alcohol, dehydrogenase. Now look at the words carefully. Do you see an ASE at the end of each word? Now when did this kind of naming system start? Well, it all started with the first enzyme that was discovered which was diastase. And to honour the scientist who first discovered the enzyme, all subsequent enzymes were named by using an ASE as a suffix. And the easiest and most popular way of doing it was to put an ASE at the end of the substrate name. Let's take the example of urease which converts urea into ammonia and carbon dioxide. Now do you see how this urease name is derived? Just by using an ASE after the substrate name, right? But the problem with these kind of names was that it didn't speak anything about the reaction it is catalysing. Well, we do understand that it must be acting on urea but nothing more than that. Just by looking at the name, can you tell that urease actually hydrolyzes? Does hydrolysis of urea in order to form ammonia and carbon dioxide? We will not be able to tell that, right? Now apart from putting an ASE at the end of the substrate, scientists were seen to put an ASE at the end of any kind of word that they felt was correct. For example, burnies. Now what do we understand by burnies? Like neither does it talk about the substrate nor about the reaction it is catalysing. By burn, we understand an outhouse, right? And burnies definitely do not hydrolyze a burn. So gradually, scientists started naming enzymes with a hint of the reaction it was catalysing. For example, glucose oxidase. Now here, the substrate name is very clear and the reaction is again very clear. It is an enzyme that does the oxidation of glucose, right? Now this was all happening somewhere around 1950s when a lot of new discoveries of enzymes were taking place. And the worst part was there was no specific rule as to how to name enzymes. And all the scientists all over the world came up with names which they thought was best, which created a lot of confusion and chaos. And scientists felt the need for some kind of method to classify and name enzymes. And that is when a group of scientists approached the international union of biochemistry and it is this union that finally established the international commission on enzymes to tackle the problem. And this commission finally classified all the enzymes that were discovered till then into six different classes. And here are the six classes. Oxidoreductases, transferases, hydro lasers, liases, isomerases and ligases. Now let's talk about each of them in detail. First is the oxidoreductase. Now you can see that I have written this name in two separate colors. Just to specify that it actually catalyses two different chemical reaction. One is oxidation and the other is reduction. It is quite prominent even from the name, right? Now what do we understand by oxidation? It can be either a gain of oxygen, a loss of electron or a loss of hydrogen, right? And the opposite is true for reduction. By reduction we mean loss of oxygen, a gain of electron or a gain of hydrogen, right? And when an enzyme does any of these things in a chemical reaction, it is categorized under oxidoreductases. It is called oxidases, reductases or dehydrogenases because it also removes hydrogen, right? Now let's look at an example, an example of lactic acid fermentation. Here lactate is getting converted to pyruvate or pyruvate can be converted to lactate. It's a reversible reaction. Now I want you to carefully look at this part of the lactate molecule which has one alcohol group attached to the carbon and an additional hydrogen. Now this lactate gives away both its hydrogen and forms a double bond with the oxygen molecule and the molecule that finally forms is called the pyruvate, okay? Now who doesn't give away both these hydrogen molecule too? It gives it away to NAD which is a cofactor or electron carrier. Now don't worry, we don't need to know about all of these in detail right now. But what's important for us to understand is that lactate here is getting oxidized by giving away both its hydrogen and then NAD on the other hand which is accepting those hydrogen is getting reduced. And any enzyme that catalyzes such a reaction in which both oxidation and reduction is taking place, it is classified under oxidoreductases. So the enzyme here which is lactate dehydrogenase is grouped under oxidoreductases. So we can summarize that oxidoreductases are enzymes that does oxidation and reduction reactions and we learn that an example is lactate dehydrogenase, right? Now let's move on to the second class of enzyme which is transferase. Now from the name transferase we can guess that it must be transferring something, right? So transferase houses a group of enzyme that transfers functional group, okay? But functional group except for hydrogen. Let's look at an example. Here we have an alanine and alpha-ketoglutarate. Now alanine transfers its amine group to alpha-ketoglutarate and thus alanine becomes pyruvate and alpha-ketoglutarate with its amine group becomes glutamate. And this reaction is catalyzed by alanine transaminase, transaminase because it is transferring in a mine group. So we got an example of transferases which is alanine transaminase, okay? Now the third class of enzyme which is hydrolysis. Here again the name speaks for itself, hydrolysis houses enzymes that does hydrolysis reaction which means breaking down of a molecule in the presence of water. Let's look at an example now. So here I have pyrophosphate molecule which in the presence of water is broken down into two phosphate molecule, okay? The enzyme that is catalyzing it is called pyrophosphatase. So an example of hydrolysis would be pyrophosphatase. And not just pyrophosphatase, there are abundance of hydrolysis in the biological system. Any enzyme that breaks down a peptide bond we call them peptidases. If it breaks down the ester bond in lipids we call them the lipases. And if it is breaking down the glycosidic bond in myelos we call them myelases. And all those comes under the hydrolysis class of enzymes, okay? Now let's move on to the fourth class of enzyme which is liases. Any group of enzyme that has the capacity to remove a group from its substrate without hydrolysis or oxidation, we group them under the liase class of enzymes. Let's look at an example now. So here is a pyruvate which loses its carbon and two oxygen forming acetyldehyde and carbon dioxide. And this reaction is catalyzed by pyruvate decarboxylase, decarboxylase because a carbon dioxide is removed from pyruvate, right? If it would have removed a water we would call it dehydrates, dehydrates. Or if it would have removed an ammonia we would call it deaminase. So we can write an example of liase would be pyruvate decarboxylase. Moving ahead to the fifth class which is isomerases. Now what do we understand by isomers? Isomers are the molecules whose molecular formula is same but their geometric arrangement is different. For example, here is a structure of Dubutene and this also is Dubutene. But here the methyl group are on the same side together but here it is on the opposite side. This is called the cis arrangement, this is called the trans arrangement. And apart from cis and trans arrangement isomers can also be of other types. For example, here we have alanine that has an amine group on its left and after rearrangement it now sits on the right. Now both of them have the same molecular formula but as their functional group is rearranged or as their geometric structure is rearranged they now have different chemical and physical properties. Now the enzyme that does all this rearrangement of atoms in order to form isomers are classified under isomerases. And here we got an example alanine resimes. Okay now it's time to move to the sixth class which is ligase. It's classified under ligases, links or binds to molecules with the help of ATP. You must have heard of DNA ligase, the enzyme that ligates to DNA strands. Okay let's look at another example. Here we have two groups glutamate and amine group and these two groups are combined by a ligase enzyme which in this case is glutamine synthetase and this enzyme with the help of ATP joins the amine group to the glutamate group thus forming glutamine. Okay so in this video we have learnt about six different classes of enzymes. Now I feel the best way to study enzymes is to study chemical reaction that goes on in living cells especially the Krebs cycle or glycolysis which is there in your syllabus. So when you study those pause at each step. Look carefully at what the enzyme is doing at that step. Is it oxidizing, hydrolyzing, ligating something and then try to place them under these classes. That way when you understand enzymes those difficult and boring chain of chemical reactions of biology will turn into something easy and fun to grasp for you.