An enzyme is a protein that acts as a catalyst for a chemical reaction by accelerating it. Enzymes are fundamental protagonists in the processes of cellular metabolism. Enzymes bind their substrate in the reactive or catalytic center, which is usually protected from water to avoid unwanted interactions. In the reactive center, the spatial arrangement and types of amino acid side chains are essential to correctly orient the substrate and interact in the desired way to carry out the catalysis of the reaction. Enzymes are very selective in relation to the substrates they modify. Enzymes tend to be much larger than their substrates and often require the participation of other smaller non-polypeptide molecules such as coenzymes (biotin, NADH among others) or metal ions called cofactors.
