Enzymes are composed of globular type proteins. The basic building blocks of proteins are amino acids. Enzymes can contain 62-2,500 different amino acids. Enzymes that are made up of only proteins are called simple enzymes. Many enzymes contain other components besides protein. Enzymes that are composed of protein and non-protein parts are called conjugated enzymes. The protein part of the conjugated enzyme is called the apo-enzyme and the non-protein part is called the prosthetic group. The apo-enzyme and the prosthetic group together are called holoenzymes. A co-factor if the prosthetic group is formed of a metal and a co-factor if it is formed of an organic chemical substance.
