Allosteric Effectors

in this video, we're going to begin our lesson on Alice Terek defectors. So at this point in our course, we already have somewhat of an idea that Alice Terek defectors are just regulatory molecules that bind to Alice Terek sites on an Alice Terek enzyme in order to regulate the Alice Terek Enzymes activity or initial reaction velocity Veena. Now it turns out that these Alice Terek defectors can really be grouped broadly into two separate categories, and these two categories are hetero Tropic Effect er's as well as Homo Tropic defectors. And so the prefix hetero means different, whereas the prefix Homo means the same and so hetero Tropic Alice Derek defectors are just molecules that affect analys Derek enzymes activity on a different molecule again, since hetero means different. And then, of course, home. A tropical hysteric effect er's are just going to be molecules that affect analys Derek Enzymes activity on that same exact molecule, since again Homo means the same. And so, in other words, when it comes to home a tropic effect, er's it's pretty much saying that the substrate itself is going to act as the Alice Derek Effect er and so all of this can be pretty confusing. So let's take a look at our example down below of Hetero Tropic versus home. A trophic effect er's to clear some of this up. And so we're going to start off with the left hand side of our image over here and notice that this red structure right here represents our Alice Terek enzyme, which is catalyzing this reaction right here, converting the substrate into the product over here and notice that this yellow molecule right here is acting as an Alice Terek effect er to regulate the Alice Derek Enzymes activity on this reaction and so notice that it's labeled specifically as a hetero tropic effect er and so up above, we can write in hetero Tropic affect er And so the reason that this yellow molecule is a hetero trip effect er and not a homo tropic effect, er is because this yellow molecule itself is acting as an analyst, Eric effect er, to affect the al hysteric enzymes activity on a different molecule, which is the substrate itself. And so essentially, what we're saying is that because the substrate is structurally a different molecule than the Alice Terek effect er that is what makes the Alice Terek effect er a hetero tropic effect. Er is because this thes two molecules are different from each other. And again, hetero means different. Now, if we compare this to the right hand side of our image over here, notice again. We have the al hysteric enzyme here catalyzing the same exact reaction. And this time noticed that the substrate itself is really acting as the Alice Derek effect. Er um, to affect the Al Hysteric enzymes activity on the same exact molecule. And so this is what makes this, uh, the homo Tropic effect er and again, the reason that it's ah, home a tropic effect is because the substrate itself is what's acting as the Alice Terek effect. Er And so now that we've introduced hetero, Tropic and Home a trophic effect er's and our next lesson video, we're going to talk about yet another way to categorize Alice Derek defectors. So I'll see you guys in that video

So, in addition to grouping Alice Derek defectors as either hetero, tropic or home a Tropic Alice Derek defectors can also be grouped into other ways based on their results, either as activators or as inhibitors. Now activators are commonly represented with a positive sign, whereas inhibitors air commonly represented with a negative sign. Now activators are going to be Alice Terek defectors that specifically stabilized the our state confirmation of the Alice Terek enzyme. And, of course, stabilizing the our state is going to increase the concentration of our state and therefore decrease the Alistair constant l not. And that's because AL not recall is just the ratio of the T state to the our state and again increasing the concentration of our state is going to decrease this entire ratio. As we mentioned here. Now, these Alice Terek defectors that act as activators as we'll see down below in our image are going to cause a shift in the sigmoid curve to the left. Now inhibitors, on the other hand, are going to be Alistair IQ activators that stabilize the T state confirmation of the Alice Terek enzyme and and, of course, stabilizing. The T state is going to increase the concentration of the T state even further. And that's going to increase the Alice Derek Constant l not, which is again. This ratio right here of the T states over the our states and so increasing the concentration of tea will increase this ratio. And inhibitors, on the other hand, are going to cause a shift in the sigmoid curve to the right as we'll see down below and our image. So in our example, down below, we're going to look at the hetero trophic effects of a T. P and C T p on the ballast Eric Enzyme Asper Tate Trans car bomb Elise or a. T. C. S for short. And so notice down below In this blue box right here, what we have is the reaction that's catalyzed by the enzyme 80 c ace. And so a tch converts carbon oil phosphate and L Asper Tate into carbon oil Asper Tate and inorganic phosphate essentially just swapping the pink here with the brown. And so notice that in green with this positive sign here, the molecule a teepee is acting as an A list Eric activator for the enzyme 80 c ase and then of course, and blue with the negative sign here, the molecule CTP is acting as an A list Eric inhibitor for the enzyme 80 c ase and so, taking a look at the enzyme kinetics plot down below notice that we have these three different curves. This black curve right here represents the enzyme catalyzed reaction of above. In the absence of any Alice Derek defectors, the green curve represents again the same exact enzyme catalyzed reaction up above except in the presence of an activator. And of course we can see that a teepee is the molecule acting as the Alice Terek activator for the enzyme a T. C. A s. Now here in blue, what we have is the the same exact enzyme catalyzed reaction of above except this time in the presence of an Alice Terek inhibitor. And of course, we know that C. T. P is the molecule acting as the Alice Terek inhibitor for the enzyme c ase and so comparing this with with what we set up above, notice that activators air going to stabilize the our state and cause a shift in the sigmoid curve to the left. And so notice that in the presence of the activator. This green curve here is shifted to the left when we compare it to this black curve in the absence of inhibitor and also noticed that we said that inhibitors are going to stabilize the T state and cause a shift in the sigmoid curve to the right. And so looking at this blue curve down below noticed that in comparison to the black curve, it is indeed shifted to the right. And so what helps me remember this shift to the left and the shift to the right is actually a completely different mindset. And so if you pick any substrate concentration that you want any particular substrate concentration and you compare the initial reaction velocities of all three of the curves, we know that activators are going to increase the initial reaction velocity with respect to the green curve. And so we expect activators to have a higher initial reaction velocity so we can imagine plotting a point here and with inhibitors. Of course, with respect to the absence of any defectors, we expect inhibitors to decrease the initial reaction velocity, so we would have a point down here. And so if you repeat this process many, many, many times, then it becomes very clear that in the presence of an inhibitor, of course it's going to be shifted to the right. And so a decreased initial reaction velocity corresponds with a shift of the curve to the right. And, of course, an increase in the initial reaction velocity is going thio correspond with a shift of the sigmoid curve to the left, as we see with the green curve. And so notice that here, uh, in this image that none of these defectors are affecting the V max of the enzyme, they're all going up to this V Max horizontal. Ask them to hear, However, uh, there are some scenarios where defectors can affect the V Max. And so, of course, uh, if an activator affect the V Max, it's going to increase the V max. Whereas if an inhibitor affects the V Max, it's of course, going to decrease the V max. And so this here concludes our introduction to Alice Terek activators and inhibitors, and we'll be able to get some practice utilizing these concepts and our next couple of practice videos. So I'll see you guys there