Inhibitors are certain compounds (Drugs, poisons) which bind with the enzymes and bring about a decrease in the catalytic activity of that enzyme.
In competitive inhibition, the inhibitor closely resembles the real substrate and is referred to as substrate analogue. Both the substrate and the inhibitor compete for binding to the active site of the enzyme. As long as the competitive inhibitor holds the active site, the enzyme is not available for the substrate to bind.
Competitive inhibition can be reversed by increasing the concentration of the substrate. In competitive inhibition, the Km value increases whereas Vmax remains unchanged.
In non-competitive inhibition, the inhibitors bind at a site other than the active site on the enzyme. The inhibitors react with various functional groups of the enzyme and disrupt their normal functioning.
Non-competitive inhibition cannot be reversed by increasing the concentration of the substrate. In non-competitive inhibition, the Km value is unchanged while Vmax is lowered.