1. Proteinous nature: Nearly all enzymes are proteins although some catalytically active RNA molecules have been identified. 2. Colloidal nature: In the protoplasm, enzymes exist as hydrophilic colloids. Due to colloidal nature, they are isolated by dialysis. 3. Substrate specificity: A given enzyme only catalyzes one reaction or a similar type of reaction. For example, maltase acts only on maltose [...]
Several theories have been proposed to explain the mode of enzyme action. (1) General Theory of Enzyme action (Enzyme - substrate complex theory): Victor Heneri (1903) first proposed that the enzyme (E) combines with substrate (S) to form enzyme-substrate (ES) complex as a necessary step in enzyme catalysis. Later, Leonor Michaelis and Maude Menten (1913) expanded this concept into a [...]
Enzymes are proteins, and therefore their capacity for catalysis is intimately related to a specific tertiary or quaternary molecular structure. If the tertiary or quaternary structure of an enzyme is altered, a loss of enzyme activity usually follows. Thus, environmental factors that modify protein structure also influence enzyme activity. Key environmental factors that can affect enzyme activity are pH and [...]