tissue-plasminogen activator BINDING

[Phloston]

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We all know that tPA helps convert plasminogen to plasmin during thrombolysis.

Anyway, I got a question in Kaplan QBank about what streptokinase binds to.

I immediately clicked plasminogen as the answer, then paused for a moment.

Now I remember having read somewhere that tPA binds to FIBRIN, not plasminogen, despite the fact that it converts plasminogen to plasmin.

So I thought this was going to be one of those "wtf" questions, where everyone thinks it's plasminogen, but the answer is actually fibrin, and only ~12% get it right.

So I changed my answer to fibrin, and what do you know, 86% got it correct, and the answer was plasminogen! (who's the ****** now? I mean seriously)

Then I flipped to the relevant section in FA, and I had specifically annotated in there, "tPA binds to FIBRIN, not plasminogen."

I'm left thinking, "do streptokinase and tPA bind to different sites? Or had I just annotated from some bogus source?"

Any thoughts?

 

[chaotic mind]

We all know that tPA helps convert plasminogen to plasmin during thrombolysis.

Anyway, I got a question in Kaplan QBank about what streptokinase binds to.

I immediately clicked plasminogen as the answer, then paused for a moment.

Now I remember having read somewhere that tPA binds to FIBRIN, not plasminogen, despite the fact that it converts plasminogen to plasmin.

So I thought this was going to be one of those "wtf" questions, where everyone thinks it's plasminogen, but the answer is actually fibrin, and only ~12% get it right.

So I changed my answer to fibrin, and what do you know, 86% got it correct, and the answer was plasminogen! (who's the ****** now? I mean seriously)

Then I flipped to the relevant section in FA, and I had specifically annotated in there, "tPA binds to FIBRIN, not plasminogen."

I'm left thinking, "do streptokinase and tPA bind to different sites? Or had I just annotated from some bogus source?"

Any thoughts?

streptokinase binds to plasminogen- which exposes an active site in plasminogen and the plasminogen then converts other plasminogen molecules to plasmin.

tpa preferentially activates fibrin bound plasminogen.
so they do bind to different sites.

 

[Phloston]

streptokinase binds to plasminogen- which exposes an active site in plasminogen and the plasminogen then converts other plasminogen molecules to plasmin.

tpa preferentially activates fibrin bound plasminogen.
so they do bind to different sites.

Where did you find that?

 

[chaotic mind]

Where did you find that?

katzung and trevors pharmacology

 

[Phloston]

I guess what I'm getting at is, on the actual USMLE, would you confide in selecting "fibrin" over "plasminogen" as the binding site for tPA?

Sorry for dragging this on...

 

[Myxedema]

Both are correct. If fibrin is among the answer choices, it's better. If not, choose plasminogen.

http://www.cvpharmacology.com/thrombolytic/thrombolytic.htm

 

[Phloston]

Thanks so much. That article is pretty much exactly what I needed to see.