BMS131 Enzymes: Structure and Function

Enzymes are typically globular proteins with specific three-dimensional structures. They have an active site where the substrate binds, and their properties include specificity for substrates and sensitivity to environmental factors such as pH and temperature.

Enzymes act as biological catalysts that lower the activation energy required for a biochemical reaction to occur, thereby increasing the reaction rate.

Factors affecting enzyme activity include temperature, pH, substrate concentration, enzyme concentration, and the presence of inhibitors or activators.

Enzymes can be classified as oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Examples include dehydrogenases, kinases, lipases, decarboxylases, mutases, and synthetases.

Enzyme regulation can occur through mechanisms such as allosteric regulation, covalent modification, and gene regulation. An example of allosteric regulation is the activation of hemoglobin by binding to oxygen.

The energy of activation is the energy required to initiate a chemical reaction. Enzymes lower the energy of activation by binding to the substrate and stabilizing the transition state, thus facilitating the conversion of substrate to product.

Enzyme inhibitors are molecules that bind to enzymes and decrease their activity. Examples of enzyme inhibitors include competitive inhibitors (e.g., statins), non-competitive inhibitors (e.g., heavy metals), and uncompetitive inhibitors. Enzyme inhibitors can disrupt the binding of substrate to the active site or alter the enzyme's conformation, leading to decreased enzymatic activity.

Plasma enzymes are used as biomarkers for diagnosing various clinical diseases. For example, elevated levels of creatine kinase (CK) in the blood indicate muscle damage, which can be associated with conditions such as myocardial infarction. Similarly, elevated levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) can indicate liver damage.

Enzyme regulation involves various mechanisms such as allosteric regulation, covalent modification, and feedback inhibition. For example, allosteric regulation can activate or inhibit enzyme activity by binding to regulatory sites, while covalent modification, such as phosphorylation, can alter enzyme conformation and activity. Feedback inhibition involves the end product of a metabolic pathway binding to an earlier enzyme in the pathway to inhibit its activity.

Enzymes are composed of amino acid chains folded into complex three-dimensional structures. The active site of the enzyme interacts with the substrate, and the enzyme-substrate complex undergoes catalysis to produce the product. The specific arrangement of amino acids in the active site contributes to enzyme specificity and catalytic efficiency.