Enzyme catalytic processes

Enzyme catalytic processes are extensively used in food industries for centuries such as in production of bread, beverages, yoghurt, cheese, vinegar etc. Enzymes have properties similar to homogeneous catalysts. New enzymes are continuously being discovered. At present, more than 3000 enzymes are reported.

Enzyme catalyst

Enzymes are large macromolecular polypeptide (polymers of amino acid monomers) proteins. Molecular weight is in the range of 104-106 . Each enzyme has unique three-dimensional structure with a binding site or active site that is chemically and geometrically compatible with particular reactant molecule and thereby can give upto 100 % selectivity.

Enzymes are formed in living systems by condensations and/or dehydrations of amino acids that have the composition of H₂N-CHR-COOH, to form peptide C-N bonds. Large structure contains hundreds of amino acids and there is enormous number of possible structure. Only few are characterized and well known. Naturally occurring metal ions in enzymes reported are Mg, Zn, Ca, Ni, Fe, Co, Mo.

Example :

• Lysozyme enzyme
• Catalyze splitting of poly saccharide chains
• 129 amino acids residues joined by peptide linkage
• Glutamic acid and aspartic acid are important functional groups at the active sites

Enzymes are synthesized by living organisms and can be extracted from their biological source, purified and used in laboratory and industrial processes. Enzymes can also be synthesized in vitro that is in artificial environment outside the living organism. Enzymes are only active within a limited range of pH and temperature.

Enzyme catalysis

• Enzyme catalyze variety of biological reactions such as:
• Breakdown of proteins and sugars
• Photosynthesis
• Oxidation –reduction that convert food to CO₂ , water and energy
• Production of hormones

Enzymes are classified into six different groups based on the type of reactions catalyzed:

1. Oxidoreductases : oxidation-reduction
2. Transferases : functional group transfer
3. Hydrolases : hydrolysis
4. Lyases : addition or formation of double bonds
5. Isomerases : isomerization
6. Ligases : bond formations

Activity

Enzymes generally function only under mild condition of temperature and pH. Activity of a typical enzyme increases with temperature upto 50-60°C passes through a maximum and then declines. Enzymes catalyze biochemical reactions with very high rates, 10-10000 molecules /enzyme/second compared to one or less for conventional catalysts. High activity of enzyme is illustrated in Table 1.

Table 1. Comparison of activation energies and relative rates of acid catalyzed and enzyme catalyzed hydrolysis reactions