How Enzymes are Activated

Enzymes are proteins that consist of sequences of amino acids gathered together by peptide bonds. An enzyme molecule can have one or more peptide bond or polypeptide chains. The sequence of amino acids within the polypeptide chains is characteristic for each enzyme and is thought to establish the unique three-dimensional structure in which the chains are composed.

This conformation, which is necessary for the functionality of the enzyme, is determined by interactions of amino acids in several zones of the peptide chains with each other and with the surrounding medium. These interactions are relatively weak and can be disrupted readily by high temperatures, acid or alkaline ambience, or alterations in the polarity of the medium. These changes lead to an unfolding of the peptide chains (or denaturation) and a subsequent loss of enzymatic activity, solubility, and other abilities characteristic of the native enzyme.

Many enzymes have an additional, nonprotein component, called a coenzyme. This can be an organic molecule, often a vitamin derivative, a metallic ion (copper and zinc for some of the enzymes in snail secretions) or an organic (usually metal-containing) group.

The coenzyme, in most cases, participates directly in the catalytic reaction. For example, it can serve as an intermediate carrier of a group being carried from one substrate to another. Certain enzymes have coenzymes that are strongly linked to the protein and difficult to remove, while others have coenzymes that dissociate readily. When the protein unit and the coenzyme are separated from each other, neither possesses the catalytic abilities of the original conjugated protein (the holoenzyme).

By simply combining the protein unit and the coenzyme together, the completely active holoenzyme can usually be reconstituted. The same coenzyme can be linked with many enzymes which catalyze different reactions. It is thus mainly the nature of the protein unit rather than that of the coenzyme which determines the specificity of the reaction.

The enzyme-cofactor couple provides an active configuration, commonly presenting an active site into which the substance (substrate) implied in the reaction can fit. Most enzymes are specific to one substrate. If a competing molecule blocks the active site or alters its shape, the enzyme’s activity is inhibited. If the enzyme’s composition is altered its activity is lost.

Enzymes are classified by the kind of reaction they catalyze: (1) oxidation-reduction, (2) transfer of a chemical group, (3) hydrolysis, (4) removal or addition of a chemical radical, (5) isomerization, and (6) joining together of substrate units (polymerization).

Enzymes catalyze all aspects of cell metabolism, including the digestion of food, in which large nutrient molecules (including proteins, carbohydrates, and fats) are divided into tinier molecules; the conservation and changing of chemical energy; and the creation of cellular elements and components.

The fermentation of wine, leavening of bread, transformation of milk into cheese, and brewing of beer are all enzymatic reactions. The uses of enzymes in medicine involve destroying disease-causing microorganisms, the treatment of injuries, and diagnosing certain ailments.

Thanks to enzymatic processes, science has been able to derive new treatments that can help repair damaged skin.

A new skin moisturizer offers the opportunity to eliminate scars, imperfections and several skin ailments thanks to a biological ingredient that repairs damaged tissue.

- Kathleen LeRoi