enzyme structure

Last reviewed 01/2018

Enzymes are fundamentally proteins; the exact amino acid sequence determines the secondary level of structure due to interaction between individual side groups:

• random
• alpha-helix
• beta-pleated sheet

Often, hydrophobic groups are hidden in the centre of a globular molecule with combinations of these structures. The enzyme forms a complex with its substrate before catalyzing its conversion to product. The reaction is usually dependent on an active centre, usually a cleft in the molecule into which the substrate passes. The shape of the active site is pivotal in ensuring that the right substrate enters in the correct orientation to be placed under strain or come into association with coenzymes.

For example, lysozyme is an enzyme which cleaves the polysaccharide in bacterial cell walls. It is a polypeptide of 129 amino acid residues which form a globular molecule with both alpha-helical and beta-pleated sheet structures. Its active centre is a cleft fitting 6 amino acids which acts to break the bond between the 4th and 5th.

Also, enzymes may come in different isoenzymes and forms. They are often reliant on co-enzymes and co-factors.