Ribbon diagram of the catalytically perfect enzyme TIM.

Enzymes are essential to sustain life because most chemical reactions in biological cells would occur too slowly, or would lead to different products without enzymes. A malfunction (mutation, overproduction, underproduction or deletion) of a single critical enzyme can lead to a severe disease. For example, the most common type of phenylketonuria is caused by a single amino acid mutation in the enzyme phenylalanine hydroxylase, which catalyzes the first step in the degradation of phenylalanine. The resulting build-up of phenylalanine and related products can lead to mental retardation if the disease is untreated. - from Wiki

Every biological reaction in our body is concering enzyme and it plays a really important role in entire environments surrounding us. It’s amazing that we don’t seriously know of the fact and I’ve just known about enzyme - which means a essential part of all about biology.