Special case of enzyme inhibitor?

Debate and discussion of any biological questions not pertaining to a particular topic.

Moderators: honeev, Leonid, amiradm, BioTeam

Post Reply
Azure
Garter
Garter
Posts: 3
Joined: Tue Feb 15, 2011 8:55 am

Special case of enzyme inhibitor?

Post by Azure » Tue Feb 15, 2011 9:01 am

How can you classify an enzyme inhibitor exhibiting an increase in both Km and Vmax values? It cannot be a competitive inhibitor (constant Vmax and increased Km), noncompetitive inhibitor (constant Km and decreased Vmax), nor uncompetitive inhibitor (decreased Km and Vmax). Is it alright to consider it a mixed inhibitor?

However, the definition for a mixed inhibitor is a combination of competitive and uncompetitive inhibitor and is expected to have an increased Km but decreased Vmax.

Moreover, how can one be able to describe the increase in maximum velocity of the enzyme? I could not find any such cases online but I can assure that this has happened and is possible.

User avatar
JackBean
Inland Taipan
Inland Taipan
Posts: 5694
Joined: Mon Sep 14, 2009 7:12 pm

Post by JackBean » Tue Feb 15, 2011 2:41 pm

could you provide the data? I don't mean the type of enzyme or your substance, just what have you measured.
http://www.biolib.cz/en/main/

Cis or trans? That's what matters.

Azure
Garter
Garter
Posts: 3
Joined: Tue Feb 15, 2011 8:55 am

Re: Special case of enzyme inhibitor?

Post by Azure » Wed Feb 16, 2011 12:39 pm

JackBean wrote:could you provide the data? I don't mean the type of enzyme or your substance, just what have you measured.

Sure. It was based from my experiment after all.

There were three trials that I performed but I will only mention one of them as they exhibited the same results.

the data is provided at this link:
http://www.adrive.com/public/e40a587f7c2aa925229088085cb227589805a4c47825947a22623b31682f7655.html

comparing the Km and Vmax values I computed from the graph, I was able to notice that they both increased compared with the control. I was told by my professor that it was the same for mixed inhibitors but was not really able to explain the reason why. I could not understand the logic behind the increase in the maximum velocity as when the Km value increased, so would the affinity of the enzyme to the substrate would decrease. as such, catalytic reactions of the enzyme would slow down, resulting in a decrease in the maximum velocity. That is the definition of a mixed inhibitor but the results proved otherwise.

Azure
Garter
Garter
Posts: 3
Joined: Tue Feb 15, 2011 8:55 am

Re: Special case of enzyme inhibitor?

Post by Azure » Thu Feb 17, 2011 11:52 am

I believe this information may prove to be useful:
The substance I used was a crude extract which I introduced into the enzyme.

Is it possible that the reason for the increase in maximum velocity be due to other compounds present in the crude extract that may have become an allosteric effector on the enzyme or competed with the substrate? If so, how can the inhibitor be classified then? As a competitive or mixed inhibitor? What may have been a possible mechanism to explain this phenomenon?

Post Reply

Who is online

Users browsing this forum: No registered users and 8 guests