An enzyme is a substance that increases the rate of a chemical reaction. The substances which take part in the reaction other than the enzyme are known as enzyme substrates. Catalysis involves the formation of an enzyme-substrate complex. The enzyme-substrate complex requires a lower amount of energy to undergo the chemical reaction than the energy required by the substrates to react on their own.
This results in many reactions able to take place in biological systems that would not occur at the temperature and pressure found in living cells.
Once an enzyme has facilitated the reaction between substrates, it returns to its original state and is ready to aid another bio-chemical reaction.
substrate in an enzymatic reaction means the substance on which the enzyme acts
example in the conversion of sucrose to glucose the enzyme is sucrase
according to latest iupac convention one can use the name of enzyme as "name of substrate+ase"