7. Enzyme Inhibition and Regulation
Phosphorylation
1
concept
Phosphorylation
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in this video, we're going to talk about yet another type of post translational modification, which is phosphor relation. So as we mentioned, fossil relation is just one of many different types of post translational modifications, and it's actually a pretty simple idea. All phosphor relation is is the covalin attachment of a phosphate group. And so it turns out that foster relation is actually one of the most common means off enzyme regulation and therefore that makes foster relation one of the most important forms of enzyme regulation. And that's why it's worth taking the time to study phosphor relation now down below and our image. We're showing you guys the simple idea of phosphor relation, where we can take any protein or any enzyme and simply add a phosphate group to the protein CO violently so that we end up getting this structure right here. And ultimately, this edition of the phosphate group to the protein can again regulate the enzymes activity. And so, in some scenarios, phosphor relation. The addition of this phosphate group will activate the protein and turn on the protein so that it can do its job, whereas in other situations, phosphor relation again the Covalin attachment of this phosphate group will inactivate the protein and turn off the protein so that it cannot perform its job. But in either scenario, what's important to know is that phosphor relation is capable of changing the protein confirmation. So notice here we have a circular red protein and then over here in blue, we have the same exact protein just in a different confirmation through this phosphor relation the Covalin attachment of this Fossey group. And so, in our next lesson video, we're going to talk about the exact source of the phosphate groups, uh, in phosphor relation. And we'll continue thio to talk more about foster relation as we move forward in our course. So I'll see you guys in our next video.
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concept
Phosphorylation
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So now that we know that phosphor relation is just a post translational modification that involves the co Vaillant attachment of a phosphate group in this video, we're going to talk about a common source of the phosphate groups in phosphor relation. And that is the high energy molecule, a teepee which I'm sure most of you guys air familiar with from your previous biology courses and so recall that a teepee is just an abbreviation for a Dina seen try phosphate and the try here means three. So we know that a Dina seen triphosphate has three phosphate groups and so that means that it has plenty of phosphate groups and it doesn't mind donating a phosphate group for ah foster relation event to occur. And so a denouncing triphosphate, or ATP molecules as well see moving forward in our course are typically going to be the source of the phosphate groups in phosphor relation. Now, when it comes to foster relation, really, there are two major classes of enzymes that we need to consider. The first are going to be kindnesses, and the second are going to be phosphate ASIS, and so kindnesses are going to be enzymes that catalyze phosphor relation reactions Essentially, kindnesses are going to be the enzymes that add phosphate groups. Whereas phosphate cases are pretty much enzymes that catalyze the exact opposite reaction of kindness is and so what they do is they completely removed phosphate groups from a substrate. And so if we take a look at our example image down below notice. On the left hand side, what we have is this red circle which represents our unfussy for related protein. So notice that there are no phosphate groups attached to it. And up above, we had this molecule here that has these three phosphate groups attached to it. And so this must be our a teepee molecule. And so again, uh, kindnesses are going to be the enzymes that catalyze fast for relation reactions. And so, uh, kindnesses are going to be able to use a teepee as a co substrate and remove ah phosphate group from the A t. P and added to the unfaithful related protein in order to get the phosphor related protein that we have on the right over here. And so I noticed that the fossil related protein has the attached the CO violently attached phosphate group. And over here, what we have is the same molecule that we had over here on the left. Except now it only has two phosphate groups instead of three, and so this makes it an A D. P molecule and a denouncing die phosphate and die actually means to On DSO noticed that the reverse reaction here, which essentially removes the phosphate group attached to the foster related protein, is catalyzed by a phosphate tastes enzyme. And so, really, the main point of this lesson is to emphasize that ATP molecules are going to commonly be the source of the phosphate groups in phosphor relation events. And so again, we'll see that a lot moving forward when we talk about different types of reactions in metabolism. And in our next lesson video, we're going to talk about exactly which amino acid residues are most susceptible to phosphor relation. So I'll see you guys in that video
3
Problem
ProblemDuring kinase phosphorylation, which phosphate group is removed from ATP in the figure below?
A
α
B
β
C
γ
D
α and β
E
β and γ
4
concept
Phosphorylation
5m
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So now that we know that phosphor relation is a very common post translational modification that involves the Covalin attachment of a phosphate group, and a common source of those phosphate groups is from ATP molecules. In this video, we're going to talk about which amino acids are most susceptible to phosphor relation. And so we already know from our previous lesson videos that some amino acids can be fuss for related. Now, when an amino acid is actually phosphor related, it makes a phosphor Oh, protein. And so all of foster protein is is just a protein that has been Foss for elated. And so it's actually estimated that about one third of all of the proteins in a eukaryotic cell are actually phosphor oh, proteins, which is actually a pretty big chunk of all of those proteins. And it goes to show how phosphor relation is such an important form of regulation of proteins. Now it turns out that amino acids that have hydroxyl groups are most susceptible to phosphor elation, and these hydroxyl groups in the are groups of these amino acids can be replaced with phosphate groups. Now recall that hydroxyl groups are also called alcohol groups. And so we remember that even though alcohol is a serious threat, we can have it in moderation and eso. A serious threat here reminds us that Syrian and threatening both have alcohol or hydroxyl groups. In there are groups. And also tire seen, we know is the other amino acid. It has an alcohol, and it's argued. And so again, these hydroxyl groups in these amino acids are groups can be replaced with phosphate groups now. It also turns out that histamine is also occasionally phosphor related as well. But it's more so phosphor related in pro carry attic organisms like bacteria and in some plants, but not so much in human cells. And so phosphor relation. Or the covalin attachment of a phosphate group to these particular amino acids makes these amino acids even mawr polar than what they already were. And that can ultimately lead to changes in the enzyme confirmation or state essentially changing the enzyme from the inactive T state to the inactive, our state, or vice versa. And so, uh, it's because these phosphate groups that are attached through foster relation, uh, they have an overall negative charge on them, and so that allows them to interact with positive charges on other groups through ionic interactions and, of course, negative charges air going to repel other negative charges. And also these phosphate groups allow for stronger hydrogen bonding. And so these phosphate groups, because they have negative charges and allow for stronger hydrogen bonding thes air reasons for how fast correlation can change in enzymes, confirmation or state and so down below in our image notice we're showing you the amino acids that can be fast for elated. So over here on the left notice that we have, uh, the same peptide backbone for all of these amino acids. And we're focusing on the are groups here that can be phosphor, elated. And so we know here what we have is a searing molecule. But because the alcohol group is replaced with a phosphate group, this is actually a phosphor Oh, searing molecule on Dhere. This one is going to be a phosphor. Oh, three inning the molecule. And then over here. Of course, what we have is a phosphor. Oh, tire scene molecule. And then last but not least over here on the far right, What we have is a phosphor. Oh, histamine molecule. And so this green background right here can help remind you guys that foster histamine is more so, um, going to be taking place in plants as well as in bacteria and not so much and humans. And so this here concludes our introduction to how amino acids can be phosphor related and as we move forward in our course will be able to get some practice utilizing these concepts. So I'll see you guys in our next video.
5
Problem
ProblemCovalent modification of an enzyme usually involves phosphorylation / dephosphorylation of:
A
Lysine residue.
B
Proline residue.
C
Serine residue.
D
Aspartate residue.
6
Problem
ProblemWhen the active site of an enzyme is phosphorylated on one of its catalytic amino acid residues, the overall _______________ charge of phosphate groups would _____________ the affinity for a polar, negatively charged substrate.
A
positive; lower.
B
negative; lower.
C
negative; increase.
D
positive; increase.
E
positive; not change.
F
neutral; not change.