- All enzymes are proteins.
- An enzyme molecule may contain one or more polypeptide chains.
- The sequence of amino acids within the polypeptide chains is characteristic for each enzyme, and is believed to determine the unique three-dimensional conformation in which the chains are folded.
- This conformation, which is necessary for the activity of the enzyme, is stabilized by interactions of amino acids in different parts of the peptide chains with each other and with the surrounding medium. These interactions are relatively weak and may be
disrupted readily by high temperatures, acid or alkaline conditions or changes in the polarity of the medium.
- Such changes lead to an unfolding of the peptide chains (denaturation) and a uncomitant loss of enzymatic activity, solubility and other properties, characteristic of the active enzyme.
- Because enzyme molecules are generally globular proteins, their shape and functions may be affected by pH changes in the aqueous environments.
- Denaturation by extremes of pH Is usually reversible, not so denaturation by heat.
Temperature increase will raise the rate of collision of enzyme and substrate molecules, thus increasing the rate of enzyme-substrate (ES) complex formation and raising the reaction rate.
- This is opposed by increased enzyme denaturation as the optimum temperature for the reaction is exceeded.