Why enzymes are substrate specific

And most enzymes are highly specific particularly to the nature of the substrate they bind to. Substrate specificity is one of the most essential distinctive features of enzyme s. Examples of enzymes showing a very high specificity are biosynthetic enzymes such as those involved in genome replication and expression. There are certain enzymes that have varying extent of substrate specificity. The cell uses specific molecules to regulate enzymes in order to promote or inhibit certain chemical reactions.

Sometimes it is necessary to inhibit an enzyme to reduce a reaction rate, and there is more than one way for this inhibition to occur. In noncompetitive inhibition, an inhibitor molecule binds to the enzyme at a location other than the active site an allosteric site. The substrate can still bind to the enzyme, but the inhibitor changes the shape of the enzyme so it is no longer in optimal position to catalyze the reaction.

Enzyme inhibition : Competitive and noncompetitive inhibition affect the rate of reaction differently. Competitive inhibitors affect the initial rate, but do not affect the maximal rate, whereas noncompetitive inhibitors affect the maximal rate.

In noncompetitive allosteric inhibition, inhibitor molecules bind to an enzyme at the allosteric site. The binding of this allosteric inhibitor changes the conformation of the enzyme and its active site, so the substrate is not able to bind.

This prevents the enzyme from lowering the activation energy of the reaction, and the reaction rate is reduced. However, allosteric inhibitors are not the only molecules that bind to allosteric sites. Allosteric activators can increase reaction rates.

This increases the reaction rate. Allosteric inhibitors and activators : Allosteric inhibitors modify the active site of the enzyme so that substrate binding is reduced or prevented. In contrast, allosteric activators modify the active site of the enzyme so that the affinity for the substrate increases.

Many enzymes only work if bound to non-protein helper molecules called cofactors and coenzymes. Binding to these molecules promotes optimal conformation and function for their respective enzymes. These molecules bind temporarily through ionic or hydrogen bonds or permanently through stronger covalent bonds. Coenzymes are organic helper molecules with a basic atomic structure made up of carbon and hydrogen. The most common coenzymes are dietary vitamins.

Vitamin C is a coenzyme for multiple enzymes that take part in building collagen, an important component of connective tissue. Pyruvate dehydrogenase is a complex of several enzymes that requires one cofactor and five different organic coenzymes to catalyze its chemical reaction. Dey , Peter J.

Butler , Ayusman Sen , and Ramin Golestanian. Nano Letters , 17 7 , Journal of Molecular Biology , 15 , Biomolecules , 10 6 , Fluctuation-induced hydrodynamic coupling in an asymmetric, anisotropic dumbbell.

Grahame Hardie , Sheng-Cai Lin. Fructose-1,6-bisphosphate and aldolase mediate glucose sensing by AMPK. Nature , , Illien , T. Adeleke-Larodo , R. Diffusion of an enzyme: The role of fluctuation-induced hydrodynamic coupling. Here's an example: When the salivary enzyme amylase binds to a starch, it catalyzes hydrolysis the breakdown of a compound due to a reaction with water , resulting in maltose, or malt sugar.

Live Science. Joseph Castro.