uncompetitive inhibitors

[aspiringmd1015]

they decrease vmax and KM, with binding to only enzyme/substrate complexes. I understand how that could maybe change KM, but why vmax?

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[aspiringmd1015]

??

 

[Reperfused]

Non-competitive inhibitors do not change Km. They only decrease Vmax.

 

[aspiringmd1015]

That's what I thought, but it says differently in uw, where it shows the X axis going farther away from 0 meaning, lower KM and lower vmax. I'm guessing uncompetitive is different that no competitive or something


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[Reperfused]

That's not what it means. Don't look at how far away from zero at the X axis it's going. Look at the y-intercept (the point at which the line is crossing the Y axis). Is it the same? That means Km is unchanged.

 

[Reperfused]

wait, I think I wrote something wrong above. Let me check

 

[aspiringmd1015]

You did, I agreed that the vmax changes, it decreases so the t intercept is going to increase, but like I said the X intercept is also shifting, and it's shifting left implying a decrease in KM, so somehow it's increasing the affinity.


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[Reperfused]

Yeah sorry my bad, I ended up writing about Vmax above. For Km you do check X intercept.

 

[Reperfused]

And a little Google search tells me that indeed non-competitive and uncompentitive are not the same. Uncompetitive decreases both Km and Vmax (as you say it's mentioned in UWorld).

 

[Reperfused]

So this uncompentitive inhibitor binds the "enzyme-substrate complex" (unlike other inhibitors that bind the enzyme) and increases the enzyme's apparent affinity for the substrate because it takes longer for the substrate or product to leave the active site of the enzyme. This apparent increase in affinity perhaps causes the decreased Km.

 

[MissNomer]

QID please?

 

[aspiringmd1015]

So this uncompentitive inhibitor binds the "enzyme-substrate complex" (unlike other inhibitors that bind the enzyme) and increases the enzyme's apparent affinity for the substrate because it takes longer for the substrate or product to leave the active site of the enzyme. This apparent increase in affinity perhaps causes the decreased Km.

i see, so its inhibiting the vmax, but increasing the affinity...hmmm. lol whats the point of that.

 

[Ven0m]

edit: nvm i misread your post