Why are enzymes pH sensitive?

[kenhung123]

I know its got something to do with ionisation of amino acids but like how does that in turn cause denaturation?

[Richiie]

Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either the substrate cannot bind to the active site or it cannot undergo catalysis.

[akira88]

A change in pH causes the tertiary structure of a protein to denature, thereby permanently changing the shape of its active site. The enzyme is denatured, and a substrate cannot bind to it anymore.

[happyhappyland]

pH can break their hydrogen bonds

[kyzoo]

A drastic change in pH distorts any ionic bonds (e.g. between COO- and NH3+) upholding the tertiary structure, as the change in pH will change the groups involved in the bond (e.g. COO- to COOH, or NH3+ to NH2). This in turn distorts the tertiary structure of the enzyme. Hence denaturation.

[Mao]

A drastic change in pH distorts any ionic bonds (e.g. between COO- and NH3+) upholding the tertiary structure, as the change in pH will change the groups involved in the bond (e.g. COO- to COOH, or NH3+ to NH2). This in turn distorts the tertiary structure of the enzyme. Hence denaturation.

This is the only correct chemistry reply in this thread. Well done.

pH can break their hydrogen bonds

To break H-bonds, the nature of O needs to change. Unless it is already a carboxyl group (in which case it would have donated the H already and it will be an ionic attraction), it will either be present as a carbonyl (C=O) or hydroxyl (OH), neither are acids nor bases, and are not affected by change in pH.

A change in pH causes the tertiary structure of a protein to denature, thereby permanently changing the shape of its active site. The enzyme is denatured, and a substrate cannot bind to it anymore.

This is more of a 'biology' response. Need more chemistry =P