Conflicting statements in EK and Kaplan

[southpawcannon]

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In regards to non competitive inhibitors when referring to enzymes, I have noticed the following:

EK: non competitive inhibitors bind NONCOVALENTLY to enzyme at a spot other than the active site

Kaplan: a non competitive inhibitor is a substance that forms strong COVALENT bonds with an enzyme and consequently may not be displaced by the addition of excess substrate.

So...who the hell has it right? Should I go to my Biology textbook from 7 yrs ago to decide?

 

[jjunior]

I think im leaning towards EK for this one. The inhibitors such as competitive, non competitive are all reversible inhibitors so that they do bind noncovalently. and the reason that an addition of excess substrate can not overcome the effect of a noncompetitive inhibitor is because substrate and noncompetitive inhibitors are binding at different site.
i would love to hear other opinions as well. 🙂

 

[benjaminl1nus]

I believe both are right, actually. Non-competitive inhibitors can be irreversible, in the case where they form a covalent bond at a site other than the active site.

Source: my knowledge

 

[southpawcannon]

I think im leaning towards EK for this one. The inhibitors such as competitive, non competitive are all reversible inhibitors so that they do bind noncovalently. and the reason that an addition of excess substrate can not overcome the effect of a noncompetitive inhibitor is because substrate and noncompetitive inhibitors are binding at different site.
i would love to hear other opinions as well. 🙂

Thank you. I'd love to hear others chime in also.

 

[N7chell]

I believe both are right, actually. Non-competitive inhibitors can be irreversible, in the case where they form a covalent bond at a site other than the active site.

Source: my knowledge

I agree that an irreversible inhibitor's mechanism is similar to that of a non-competitive inhibitor (both bind to somewhere other than the active site), but I don't think irreversible inhibitors can technically be classified as a type of non-competitive inhibitor.

With that said, I'd say EK is correct. Non-competitive inhibitors should be reversible, so it should bind to enzymes noncovalently.

 

[gettheleadout]

I believe both are right, actually. Non-competitive inhibitors can be irreversible, in the case where they form a covalent bond at a site other than the active site.

Source: my knowledge

Kaplan's statement is still too general for that special case to justify the wording. Not all noncompetitive inhibitors are irreversible inhibitors, and most encountered are reversible.

I agree that an irreversible inhibitor's mechanism is similar to that of a non-competitive inhibitor (both bind to somewhere other than the active site), but I don't think irreversible inhibitors can technically be classified as a type of non-competitive inhibitor.

With that said, I'd say EK is correct. Non-competitive inhibitors should be reversible, so it should bind to enzymes noncovalently.

Actually that's not always true. Suicide inhibitors are a particular type of irreversible inhibitor that binds at the active site, so they're actually competitive irreversible inhibitors.

EK's statement is more correct than Kaplan's.

 

[southpawcannon]

So EK seems to get the majority nod. That being said, should I worry more about EK than Kaplan? I'm studying both together in case something isn't covered in EK or is explained a bit more in depth. If there is another discrepancy, is EK more accurate than Kaplan?

 

[gettheleadout]

So EK seems to get the majority nod. That being said, should I worry more about EK than Kaplan? I'm studying both together in case something isn't covered in EK or is explained a bit more in depth. If there is another discrepancy, is EK more accurate than Kaplan?

I would just keep doing what you're doing. I'm combining EK, TBR, and the Kaplan Bio Review Notes book all for Bio.