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Why does changing certain amino acids which aren't a part of the active site

Why does changing certain amino acids which aren't a part of the active site also prevent the functioning of enzymes?

Because changing those amino acids may affect the way the protein folds into its tertiary structure, so can indirectly affect the structure of the active site.

OP

Original post by Philbert

Because changing those amino acids may affect the way the protein folds into its tertiary structure, so can indirectly affect the structure of the active site.

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

Original post by SANTR

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

Depends on the enzyme.

anosmianAcrimony

Original post by SANTR

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

Proteins contain amino acids that have carboxylic acids and amines in their R groups, and these are often important in determining the shape of the enzyme. Changing the pH usually changes the protonation of these groups - lowering the pH will cause the addition of H⁺ ions to some of them, and raising the pH will cause H⁺ ions to dissociate from them. This changes the way those groups interact with the rest of the protein, and hence the protein's shape.

Original post by SANTR

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

Haven't done biology in a while so I might be wrong but some of the bonds like ionic bonds will be disrupted by the presence of H+ ions or lack of them. Which in turn change the overall tertiary structure and therefore the active site.

Original post by SANTR

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

A significant fluctuation in pH alters the charges and prevents the substrate from locking onto the active site methinks.

Original post by SANTR

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

pH scale is a measure of H+ ions within a substance, so pH affects bonds between differently-charged amino acids in different parts of the enzyme molecule, which can affect the active site.

Do you not have any biology text books from your school?

Original post by SANTR

Ah I see. Do you know how lowering the pH for instance, affects the enzyme?

It's all about equilibria. If you have a basic amino acid, e.g. arginine, and you lower the pH of the environment to below the pKa of arginine, it will become ionised. If you have an acidic amino acid, e.g. glutamate, and you lower the pH of the environment to below the pKa of glutamate, it will become unionised. Both of these changes in ionisation will affect the ionic bonds that hold the tertiary structure of the polypeptide together, and thus, could potentially change the three-dimensional conformation of the active site, affecting the activity of the enzyme.

Original post by SANTR

Why does changing certain amino acids which aren't a part of the active site also prevent the functioning of enzymes?

Because different bonds will form, resulting in a different tertiary structure, hence making the substrate no longer complementary to the enzyme. An enzyme substrate complex won't form and a product won't be created.

Lowering the pH means adding more H+ ions to the solution, and these will form ionic bonds with the enzyme, again, forcing its tertiary structure to change into something no longer complementary to the substrate. Of course, this is beneficial to certain enzymes, like pepsin that works at a pH of 2. This is not so good with trypsin, for example, which works at a pH of 8. Its shape will be denatured and it won't work anymore.

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