Short Notes on Key Enzyme Terminologies
a) Characteristics of Enzymes
Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process. Key characteristics include:
- Specificity: Each enzyme acts on a specific substrate due to the unique shape of its active site.
- Efficiency: Enzymes can greatly accelerate reactions, often by a million times or more.
- Reversibility: Enzymes can catalyze reactions in both forward and reverse directions.
- Sensitivity: Their activity is influenced by temperature, pH, and substrate concentration.
- Catalytic nature: Enzymes are not used up in the reaction and can be reused multiple times.
b) Apoenzyme
An apoenzyme is the protein portion of an enzyme, which is inactive on its own. It requires a non-protein component called a cofactor (which can be a metal ion or an organic molecule) to become active. The combination of an apoenzyme and its cofactor forms the holoenzyme, which is catalytically active.
c) Coenzyme
Coenzymes are organic molecules, often derived from vitamins, that assist enzymes during the catalysis of reactions. They are not permanently attached and can move between enzymes. Examples include NAD+ (derived from niacin) and FAD (from riboflavin). Coenzymes often act as carriers of electrons, atoms, or functional groups.
d) Turnover Number
The turnover number (also known as kcat) is defined as the number of substrate molecules converted into product by one enzyme molecule per unit time, when the enzyme is fully saturated with the substrate. It measures the catalytic activity of an enzyme. A high turnover number indicates an efficient enzyme.
Conclusion
Understanding these basic terms is essential in the study of enzyme kinetics and function. They provide insight into how enzymes operate, their structural components, and how their activity can be quantified and enhanced.