Structural Biochemistry/Enzyme Catalytic Mechanism/Introduction

Enzymes are proteins that can accelerate biochemical reactions. They can transfer energy forms. Their functions of catalyze are very specific. They only catalyze certain reactions and when certain substrates are present. They usually do not have side products. It is important to understand that enzyme only fasten the reaction but not change the reaction equilibrium. In other words, with the presence of the enzyme, the reaction proceed thousands times faster, but the amount of final products are the same as without the presence of the enzyme.

The catalytic activity usually depends on the presence of cofactors, which is not a protein. An enzyme is called apoenzyme if it is not bound to cofactors; An enzyme is called holoenzyme if it is bound to cofactors. Cofactors are divided into two groups: metal and coenzymes. Metal cofactors can catalyze in many ways. They can ease the formation of nucleophiles, stabilize intermediates, and link enzymes and substrates. Coenzymes are small organic molecules. They can be bound to enzymes tightly or loosely. They are called prosthetic groups if they are bound to enzyme tightly.