The effect of pH on enzymes?

[no steez]

Can someone direct me through the specific effect of pH on enzymes? Thanks

[Aurelian]

Extreme pHs can denature enzymes so that they lose their tertiary structure (mainly by disturbing hydrogen bonds within the protein). Since an enzyme's function is closely linked to its overall 3D structure (i.e. its tertiary structure), this denaturing can lead to the destruction of an enzyme's activity.

Does that help? =)

[psyxwar]

Can someone direct me through the specific effect of pH on enzymes? Thanks

Extremities in pH can denature an enzyme through destroying the ionic bonds in the protein's tertiary and quaternary structures* (because those of pH extremities either have a high amount of H+ or OH- ions, which affects the ionic bonds in the protein). Denaturation destroys the shape of the enzyme resulting  in a loss of function (if the shape of the active site changes, then the enzyme isn't able to bind to its substrate(s) and therefore is unable to perform its function).

EDIT: *I think these by extension then destroy the hydrogen bonds?

[alondouek]

Following on what Aurelian (correctly) stated; examiners require you need to mention specifically that it is the distortion of the shape of the enzyme's active site that affects its ability to interact with its specific substrate.

[no steez]

Extreme pHs can denature enzymes so that they lose their tertiary structure (mainly by disturbing hydrogen bonds within the protein). Since an enzyme's function is closely linked to its overall 3D structure (i.e. its tertiary structure), this denaturing can lead to the destruction of an enzyme's activity.

Does that help? =)

Wonderful and fairly in depth explanation.
Thanks for the quick response, and thank you everyone else!

[Yacoubb]

I know its already been answered, but I'd like to have a go so I can sort of consolidate it too Hope you don't mind, hehe.

When an enzyme is exposed to a pH considered an extremity (i.e. beyond the optimum pH), the tertiary structure of the enzyme, critical to its function, is distorted by the disruption of hydrogen bonds that affects the shape of the active site. By damaging the active site, the enzyme can no longer complement its substrate and enzyme activity diminishes. We say that the protein has denatured when the pH it is exposed to is an extremity. E.g. pH of 6 for an enzyme is optimum, and we place the enzyme in a pH of 14, very alkaline solution. The denaturation of enzyme will occur + enzyme activity diminishes.

[Snorlax]

Extreme pHs can denature enzymes so that they lose their tertiary structure (mainly by disturbing hydrogen bonds within the protein). Since an enzyme's fu
nction is closely linked to its overall 3D structure (i.e. its tertiary structure), this denaturing can lead to the destruction of an enzyme's activity.

Does that help? =)

Does extreme temperature denature enzymes like this too?

[Yacoubb]

Does extreme temperature denature enzymes like this too?

Enzymes denature at any pH that is an extremity, relative to the optimum pH (i.e. above or below the optimum pH by a lot). However, we only say that enzymes denature in terms of temperature when the temperature increases to a temperature far greater than the optimum temperature (i.e. far above the optimum temperature).

So summary:

pH - denaturation at any extremity pH, high or low.
temp - denature at temperatures far greater than optimum temperature

[Shenz0r]

Does extreme temperature denature enzymes like this too?

That's right. You're breaking all the intermolecular bonds (i.e hydrogen bonds) within the secondary and tertiary structures when you have high temperatures, and so the enzyme becomes denatured and it is unable to function properly. It explains why there is a sudden drop of enzyme activity after the critical temperature has been reached.



When pH is involved, the story is a bit different.

In order to maintain a constant level of pH, amino acids in the enzyme will donate or accept hydrogen ions, so that the pH level is stabilised. However, this changes the intermolecular bonds that form between the secondary and tertiary structures (as you've pretty much changed the chemical structure of the amino acid), and hence the protein will denature.

The curve for pH affecting enzyme activity resembles a bell-curve because the pH scale is a logarithmic scale, which means that it goes up in factors of 10 (pH 6 is 10 times more acidic, and has 10x more hydrogen ions than pH 7), and so the drop in enzyme activity is not as dramatic as temperature.