Inhibitors of enzymes can be either reversible or irreversible. The most common reversible

Enzyme inhibitors are certain chemical substances that bind to enzymes and reduce the activity of the enzyme. There are two main types of inhibitors, competitive and non-competitive.
Competitive inhibitors bind to the active site (the place where the substrate binds) and therefore the substrate cannot bind.
Non-competitive inhibitors bind to a location different from the active site called the allosteric. These results in a change of shape in the enzyme and the enzyme cannot bind to the substrate.
Noncompetitive inhibitors bind to the enzyme to reduce its activity with or without the substrate.
They do not compete with the substrate in binding to the enzyme surface. They are irreversible.
They reduce the maximum velocity of the reaction while keeping the Km value constant.
For example — cyanide inhibits the action of cytochrome oxidase in mitochondria through noncompetitive inhibition mechanism.