Enzyme Kinetics

[deleted895568]

Can someone please explain this the World explanation did not make a lot of sense

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[pretty_positron]

Using POE, I know that the major difference between reversible and irreversible inhibition is that irreversible involves strong covalent bonds. This means A and D are out. From the graph, you can see that more inhibitor is required for the same activity if it is not pre-incubated, so B is out.

You should know, however, that for irreversible inhibition, the kinetics are not dependent on Km values but rather on how long the enzyme in question has been pre-incubated with the irreversible inhibitor. So there's something called kobs which is essentially the plot of enzyme activity vs. time, which when plotted logarithmically resembles first-order decay. So you use kobs/ as the x-axis rather than Km.

Basically, just know that for irreversible inhibition, that kinetics are time-dependent, so you cannot use MM kinetics to describe them. Also, you cannot recover enzyme activity by diluting out the inhibitor. You can only synthesize more enzyme.

 

[esob]

This may sound stupid, but you deduced that it was irreversible because there was a difference in activity between the pre-incubated and non-incubated samples? I follow your POE as long as there is something in that graphic that lets me know it is irreversible.

 

[pretty_positron]

This may sound stupid, but you deduced that it was irreversible because there was a difference in activity between the pre-incubated and non-incubated samples? I follow your POE as long as there is something in that graphic that lets me know it is irreversible.

What's up? I didn't know it was irreversible. I just knew B was wrong because the graph shows that for no preincubation that more inhibitor is required (x-axis) for the same activity (y-axis). Therefore, B is false. C is the only one that is left.

I had to read up on irreversible inhibition because I didn't know jack about it beforehand.

 

[esob]

What's up? I didn't know it was irreversible. I just knew B was wrong because the graph shows that for no preincubation that more inhibitor is required (x-axis) for the same activity (y-axis). Therefore, B is false. C is the only one that is left.

I had to read up on irreversible inhibition because I didn't know jack about it beforehand.

Right, I get that B is wrong, but I was just wondering how you deduced that A was wrong. What was it about the information presented that would allow someone to distinguish between A and C?

 

[pretty_positron]

Right, I get that B is wrong, but I was just wondering how you deduced that A was wrong. What was it about the information presented that would allow someone to distinguish between A and C?

A and D are saying the same things. A reversible inhibitor forms weak bonds. An irreversible one forms strong (often covalent) bonds.

Whenever you see two choices that are essentially saying the same thing they are both wrong.