Inhibitors help!

Ok, well i was taught that there are 2 types of inhibitors, competitive and non competitive and they both can be reversible or irreversible (depending on how strongly they bond). My text book on the other hand says that competitive inhibition is only reversible and if something binds permanently to the active site, its called non competitive irreversibe inhibition. :confused:

I thought non competitive means it binds somewhere other than the active site. Anyone wanna clear this up for me or will i end up going into my exam tomorrow very confused lol :p:

thanks xx

Reply 1

Prometheus

I think you're right n the books wrong, but just to clarify (as I understand it)
Competitive inhibitors bind to the active site on an enzyme
Non competitive inhibitors bind somewhere else on the enzyme, changing the active site

Of these two types, you can have reversible and irreversible inhibitors (which is what you wrote). Hmmm, odd...

Reply 2

theunforgiven

i thought when the non-competitive inhibitors attach to the ezyme they change its active site which makes the enzyme denatured and so is non-reversible. while with a competitive one they just attach to the active site...or something like that. correct me if i m wrong please

Reply 3

Prometheus

Well possibly, I think this is a case of "the truth is far too complicated", and i don't like that cos it could mean if you research it and find the real answer, and put it you get no marks, which is why I'm not. Hmmm i dunno

Reply 4

Pink Sparkles

^^ yeah i think they're not really telling us what's actually going on. Im just gonna hope it doesn't come up on the exam *prays*

Thanks both of you for replying :smile:

Reply 5

Revenged

Prometheus

Competitive and non-competitive inhibitors are types of reversible inhibitors...

Reply 6

mfb3000

Really? I thought that Carbon Monoxide binding with Haemoglobin was competing with the oxygen binding with said Hb, yet thats irreversible.

Reply 7

Revenged

Lewi

Really? I thought that Carbon Monoxide binding with Haemoglobin was competing with the oxygen binding with said Hb, yet thats irreversible.

That would just be irreversible inhibition...

Competitive and non-competitive inhibition are types of reversible inhibition, and as you said, carbon monoxide binding is irreversible...

Reply 8

mfb3000

It's also a competitive reaction though...

Reply 9

TOSCS

A non-competitive inhibitor binds somewhere other than the active site - this causes structural distortion (somewhat of a ripple effect) which changes the shape of the active site, thereby denaturing it.

Could someone tell me if I'm right?

Reply 10

Helenia

I think that the reason it's called non-competitive, even if it binds to the active site, is that it is permanent, and can't be competed off by another molecule. A competitive inhibitor only binds temporarily to the active site, and if a molecule of the normal substrate comes along, it may either knock off the inhibitor, or wait till it dissociates and then take its place - the rate of both of these is dependent on concentration.

If, however, the inhibitor is covalently bound to the active site, then no matter how much substrate there is and how much energy it has, it can't compete off the inhibitor molecule. Hence non-competitive. Though it's dodgy terminology; I would say something like "X binds irreversibly to the active site, inactivating the enzyme permanently."