Life sciences · Reference
What is an enzyme?
An enzyme is a biological catalyst, usually a protein, that speeds up a specific chemical reaction in a living organism by lowering the energy needed for the reaction to proceed.
Biological catalysts
Enzymes are catalysts: they speed up chemical reactions without being used up, so a single enzyme molecule can act on many substrate molecules in turn. Most enzymes are proteins, though some RNA molecules (ribozymes) also have catalytic activity. By lowering the activation energy needed for a reaction, enzymes allow processes that would otherwise be far too slow to proceed rapidly at the temperatures found in living cells.
Active site and specificity
Each enzyme has an active site, a precisely shaped pocket where the substrate binds. The fit between enzyme and substrate gives enzymes their specificity: a given enzyme typically catalyses only one reaction or a narrow set of related reactions.
When the substrate binds, the enzyme stabilises the reaction’s transition state, the products form, and they are released, leaving the enzyme free to act again. Enzyme activity can be influenced by temperature, pH, and regulatory molecules.
Why enzymes matter
Enzymes drive virtually every chemical process in living organisms, from copying DNA and building proteins to releasing energy from food. Examples include DNA polymerase, which builds new DNA strands, and the many digestive and metabolic enzymes that break down and assemble molecules. Without enzymes, the reactions that sustain life would be far too slow to support a living cell.
Enzymes in research and biotechnology
Enzymes are essential tools in molecular biology and biotechnology. The polymerase chain reaction, for instance, depends on a heat-stable DNA polymerase (Taq polymerase), and restriction enzymes that cut DNA at specific sequences are central to recombinant DNA techniques. Standardised naming and classification of enzymes (the EC number system) supports clear, reusable description in the literature and databases.
Key facts
At a glance
- Definition: a biological catalyst, usually a protein
- Function: speeds up a specific reaction
- Mechanism: lowers the activation energy
- Key feature: substrate binds at the active site
- Property: highly specific, not consumed by the reaction
- Classification: EC number system
Common questions
FAQ
What do enzymes do?+
Enzymes speed up specific chemical reactions in living organisms by lowering the activation energy required. They bind their substrates at an active site, help convert them to products, and are released unchanged to act again.
What are enzymes made of?+
Most enzymes are proteins, made of chains of amino acids folded into a precise shape that includes the active site. A few enzymes are made of RNA and are called ribozymes.
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