So at this point, we already know that there are four major types of enzyme catalysis, and we already covered the first three, which are general acid base catalysis, electro static catalysis and metal ion catalysis. And so, in this video we're gonna cover the fourth and Final One, which is co Vaillant catalysis. And so Covalin Catalysis is when a transient temporary co Vaillant bond forms between the enzyme and the substrate to form an intermediate molecule. And even though an extra intermediate molecule is produced and there's a longer pathway, there's still and overall increased reaction rate in comparison to the uncap it'll ized rate now. Typically, the way that Covalin Catalysis works is that enzymes can use amino acids that act as nuclear files, which recall from your previous organic chemistry courses are just atoms or molecules that have extra electron density that they can donate. And these nuclear filic amino acids that the enzymes have can attack substrates, which would be the electro filic centers, which are opposite of nuclear files. They have less electron density. And so what's really important to note is that any Covalin bonds that form with the enzyme must eventually be broken in order to restore the original enzyme. Because, remember, enzymes are not going to be consumed by the reaction and so down below, in our example, we're going to take a look at co Vaillant, Catala, sis and notice. Here we have an uncapped allies reaction at the top, and this reaction is showing a substrate which has component A and B that air co violently attached to each other and notice that at the end we have substrate. We've converted the substrate into the products where they are no longer co violently attached. And so this reaction is just a hydraulics ISS reaction and down below. You can see the mechanism for this reaction or an example of the mechanism for this reaction and so down below in this space, in this box notice, we're showing the enzyme catalyzed reaction and again this enzyme is going to be performing Covalin catalysis and essentially, what you'll see is that the substrate is exactly the same, and the products are also exactly the same. And the only difference is that there's an enzyme that's involved, and so you can see that our enzyme can have an amino acid that acts as a nuclear file. And so here it's acting as a nuclear file, and it's attacking this Carbonnel group. And ultimately, even though there's an additional step here. So even though there's this additional step, uh, the overall rate of this enzyme catalyzed reaction is still faster than the uncapped allies reaction. And so moving forward, we're gonna be able to see some examples of enzymes that utilize Covalin catalysis such as chemo trips in. But for now, this concludes our lesson on Covalin catalysis, and I'll see you guys in our next video.
2
Problem
Problem
An enzyme has two key catalytic residues, Glu 35 (pKa= 5.9) and Asp 52 (pKa= 4.5). Which of the following is likely true about the mechanism for this enzyme if the optimum pH = 5.2?
A
Glu 35 is more likely a nucleophile than Asp 52.
B
Glu 35 is more likely a general acid than Asp 52.
C
Both a and b are true.
D
a, b & c are false.
3
Problem
Problem
Which of the following mechanisms is not used by enzymes for catalysis?
a) General Acid-base catalysis.
b) Induced fit of enzyme to transition state.
c) Destabilizing the transition state.
d) Providing complementary electrostatics.
e) Binding of metal ions.
f) Specific Acid-Base Catalysis
g) a & c.
h) c & f
i) b, c & f
A
General Acid-base catalysis.
B
Induced fit of enzyme to transition state.
C
Destabilizing the transition state.
D
Providing complementary electrostatics.
E
Binding of metal ions.
F
Specific Acid-Base Catalysis
G
a & c
H
c & f
I
b, c & f
4
Problem
Problem
Which catalytic mechanism uses an electrophilic cofactor to stabilize a negative charge on an intermediate?
A
Acid-base catalysis.
B
Electrostatic catalysis.
C
Covalent catalysis.
D
Metal ion catalysis.
5
Problem
Problem
Which of the following catalytic mechanisms proceeds via noncovalent interactions?
A
Acid-base catalysis.
B
Electrostatic catalysis.
C
Covalent catalysis.
D
Metal ion catalysis.
E
b and d.
F
a, b & d.
6
Problem
Problem
Suppose that the covalent catalytic mechanism of an enzyme depends on a single active site amino acid (Cys), whose pKa = 8.3. A mutation in a nearby amino acid residue of the enzyme only slightly alters the microenvironment so that the pKa of the Cys residue increases to 10.3. Would this mutation cause the enzyme-catalyzed reaction rate to increase or decrease? Explain.
