Enzymes have these key characteristics: 

• They are proteins with a specific sequence of amino acids that fold upon themselves, forming a specific globular structure
• Increase the rate of chemical reactions by lowering the activation energy of the reaction 
• Remain unchanged after catalyzing a reaction 
• Can be used repeated for similar reactions due to the fact that they remain unchanged 
• Are specific in their actions and catalyze only specific chemical reactions due to the complementary fit between the enzyme's active site and the substrate
• The presence of an enzyme in a cell does not interfere with chemical reactions other than its own because it is specific to its reaction
• Are required in minute amounts to speed up chemical reactions, with a typical enzyme being able to catalyze about 100 to 10,000 substrates into products a second 
• Are affected by temperature with peak efficiency at a specific temperature
• Are affected by pH with peak efficiency within a specific pH range
• Can get denatured and lose their structure in extreme high temperatures or extreme pH
• Their catalytic activity can be inhibited by adding certain substances called inhibitors