enzyme question

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rosieburk
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enzyme question

Post by rosieburk » Fri Mar 14, 2008 10:18 am

does tertiary and/or the quaternary structure of a protein determine it's catalytic function? and can u explain

blcr11
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Re: enzyme question

Post by blcr11 » Fri Mar 14, 2008 2:10 pm

I guess the best answer is “maybe”. Not all enzymes have quaternary stucture. Since it is defined as interactions between different subunits, only enzymes composed of subunits can have such structure. It’s an oversimplification, but the tertiary structure refers to the overall 3-dimensional fold, and it is this which determines the function or activity of a protein.

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Re: enzyme question

Post by rosieburk » Mon Mar 17, 2008 11:04 am

Thanks blcr11, more questions

1. If you were to do an experiment to graph the effect of various substrate concentrations, would have on reaction rate and concentration of product, how would u describe the graph.
(i know it go up and eventually reaches a plateau, but how would you describe this, i don't know what to say, it needs to be quite extensive?)

2. How would a higher enzyme concentration affect the reaction rate graph?

3. If you were to design a molecule which would reduce the activity of a enzyme what would be the main characteristics of this molecule be?

no more questions

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Post by blcr11 » Mon Mar 17, 2008 3:02 pm

The usual enzyme velocity vs concentration curve is sigmoidal. Michaelis-Menten kinetics gives a velocity curve:

v = Vmax[S]/([S] + Km)

The plateauing occurs as [S] gets much greater than Km, at which point the velocity curve reduces to v = Vmax and there is no further increase in enzyme velocity with any further increase in substrate concentration. Vmax, though, is related to the total amount of enzyme in the reaction. The more enzyme there is, the greater is Vmax, up to the point where the enzyme is no longer soluble.

Increasing the amount of enzyme doesn't typically change the shape of the curve. It increases the maximum velocity. Enzyme substrates and products bind to the active site of an enzyme for whatever chemistry the enzyme does.

Most inhibitors look something like a substrate or a product molecule so that they can bind to the enzyme, but don't react.

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