Nature of Enzymes

On the basis of their chemical composition, enzymes fall into two categories: purely proteinaceous enzymes, which are made of protein alone (e.g. the proteases, which split proteins), and conjugated enzymes, which are built from a protein combined with an attached non-protein prosthetic group.

Enzymes are further distinguished by where they act: an enzyme that acts inside the very cell in which it was synthesised is called an endo-enzyme (e.g. the enzymes made in the chloroplast and mitochondrion); an enzyme that is released and acts outside the cell that made it is called an exo-enzyme (e.g. the enzymes secreted by many fungi). Notably, such enzymes retain their catalytic ability even after being extracted from the living cel …