Enzymes are Macromolecular Biological Catalysts.
The oldest recorded example to the commercial use of enzymes may be found in a description of the wine making practice in the Codex of Hammurabi (ancient Babylon, circa 2100B.C.). Ancient people already learned to use microorganisms as enzyme sources in fermentation. This activity spread all around the world, not limited to ancient Babylon, but also known in the early civilizations of Rome, Greece, Egypt, India, and China. Another oldest use of the enzymes was for the dairy products: people stored fresh milk for any reasonable length of time in multiple animal stomachs, which contains enzymes called “rennet” that can turn milk into cheese.
These are good examples of how enzymes work as biological catalysts, which means that they increase the rate of a biological reactions. And the word "enzyme" is derived from Greek, en (in) +zyme (ferment).
The Composition of Enzymes.
Enzymes are generally proteins, acting alone or in a large complex with other enzymes. Like all other proteins, enzymes are built with amino acids structured in a long chain which folds to generate specifically ordered three-dimensional structures. Each enzyme consists of between a hundred and up to a million amino acids placed like pearls on a string. The structure and function of an enzyme is decided by the order of the amino acids, or the sequence. The unique three-dimensional structure of each enzyme determines the function of the enzyme. Even slight changes in the sequence of the amino acids could have a huge impact on the three-dimensional structure and function of the enzyme. Note that only a small number of enzymes are not proteins but is composed of small catalytic ribosome nucleotide molecules, explicitly RNA’s.
Some enzymes can play their catalytic functions without help, while some enzymes require another non-protein component that is called a cofactor. Cofactors may be inorganic ions such as Mg2+ or Zn2+, or consist of organic or metallo-organic molecules which are also known as co-enzymes.
What Makes Enzymes Special.
Although enzymes are large molecules made up with hundreds to millions of amino acids, only a small part of an enzyme actually participates in the catalysis of biochemical reactions, which is called the “active site”. The three-dimensional structure of an enzyme decides the appearance and properties of the active site. The shape of the biological substrate, which is defined as the material catalyzed by an enzyme, needs to be accommodated by the active site precisely before a reaction could take place. The enzyme and substrate fit each other like a key in a lock, and only substrates with the right shape will be transformed by the enzyme. This is what makes enzymes specific in their actions. The figure below shows a schematic chart of how an enzyme catalyzes and converts the substrate into products.
How Are Enzymes Classified.
According to the type of reactions that the enzymes catalyze, enzymes are classified into six categories, which are oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Oxidoreductases, transferasesc and hydrolases are the most abundant forms of enzymes. Individual enzymes are further classified systematically based on the chemical name of the substrate and its reaction mechanism. Enzymes are also indexed with letters and numbers: the letter EC plus four numbers representing four elements. For example, L-xylulose reductase is named as EC184.108.40.206.