Enzyme

From ArticleWorld

Enzymes are molecules which are made of protein that catalyze biological chemical reactions. They are necessary to life because without them reactions in organisms would occur too slowly to allow life or would result in the synthesis of different products. An enzyme functions by lowering the activation energy of a process and allowing the reaction to proceed faster. Enzymes like other non-biological catalyst are not altered by the reactions are can continue the reaction. Of importance with enzymes however is their specificity as compared to catalyst.

Structure

The function of an enzyme is determined by its structure. There are two major structural types. These are the monomeric protein with only one polypeptide chain and the oligomeric protein with several polypeptide chains. Enzymes are produced as long chains of amino acids which fold into a three dimentional structure. Enzymes due to this folding are easily denatured by heat which destroys this folding. The majority of enzymes are larger than the substrate they act upon and so the region where the substrate binds to the enzyme is called the active site of the enzyme. Molecules known as coenzymes are sometimes necessary for catalysis of some reactions and these may also bind to enzymes at particular points. There are also sites on enzymes that may regulate the reaction by binding with the products to either increase or decrease the enzyme's activity.

Inhibition

Inhibition of enzymes can occur in several ways. These are as follows:

• Competitive inhibition – where the inhibitor binds reversibly to the substrate binding site preventing substrate binding.
• Non-competitive inhibition – where the inhibitor binds, usually irreversibly, to another part of the enzyme other than the active site.
• Partial competitive inhibition – similar to non competitive inhibition but the inhibitor and enzyme complex has some catalytic activity.
• Uncompetitive inhibition – is when the inhibitor only binds to the enzyme substrate complex but not the enzyme on its own.
• Mixed inhibition – occurs when the inhibitor can bind to both the free enzyme and the enzyme substrate complex.