What Are Enzymes and How Do They Work?

High school textbooks say that most enzymes are proteins. This sentence is not comprehensive, and you can't know this fact just by deduction—enzymes are not only proteins, but also RNases.

What is an enzyme?

Enzymes are defined as macromolecules capable of catalyzing biochemical reactions. In this type of chemical reaction, the starting molecule is called the substrate. The enzyme interacts with the substrate and converts it into a new product.

The name of an enzyme usually comes from its substrate or the chemical reaction catalyzed by it. It is named by the combination of "substrate name + enzyme (suffix)" (in English, the word for enzyme ends with -ase), such as protease, urease, amylase, lactase, alcohol dehydrogenase and DNA polymerase, etc. Different enzymes that catalyze the same chemical reaction are called isoenzymes.

Almost all metabolic reactions in the body rely on enzymes, so that the reaction can proceed fast enough to function and maintain life.

A chemical substance called an activator can enhance the activity of an enzyme, while an inhibitor can reduce the activity of an enzyme. The study of enzymes is called enzymology.

The International Union of Biochemistry and Molecular Biology has developed an EC number for enzymes; each enzyme is described by a four-digit sequence preceded by "EC", "EC" stands for "Enzymology Committee". The first number categorizes enzymes broadly according to their mechanism.

The top-level classification is:

EC 1, oxidoreductase: catalyze oxidation/reduction reaction

EC 2, transferase: transfer a functional group (such as methyl or phosphate)

EC 3, hydrolase: catalyze the hydrolysis of various bonds

EC 4, Lyase: In addition to hydrolysis and oxidation, it can also cleave various chemical bonds

EC 5, Isomerase: catalyzes changes in isomerization in a single molecule

EC 6, ligase: connect two molecules with a covalent bond.

Enzyme working mechanism

Enzymes work by reducing the activation energy required for chemical reactions to occur. Like other catalysts, enzymes will change the balance of the reaction, but will not be consumed during the reaction. Some enzymes can increase the conversion rate of substrates into products millions of times. An extreme example is orotate deoxynucleoside 5'-phosphate decarboxylase, which enables a reaction that takes millions of years to occur in milliseconds.

Although most catalysts can act on many different types of reactions, a key feature of enzymes is that they are specific.

In other words, an enzyme that catalyzes a specific reaction has no effect on other reactions. For example, amylase cannot hydrolyze cellulose, so cellulose cannot be digested and absorbed in the human body. It is the specificity of enzymes that allows organisms to proceed in an orderly manner.

The specificity of enzymes comes from their unique three-dimensional structure. Most enzymes are globular proteins that are much larger than the substrates they interact with. Their size ranges from 62 amino acids to more than 2,500 amino acid residues, but only part of the structure is involved in catalysis.

This enzyme has an active site, which contains one or more binding sites for the substrate to be oriented in the correct configuration, and a catalytic site, which reduces the activation energy. Part of the molecule. The main function of the rest of the enzyme structure is to provide the active site to the substrate in the best possible way. There may also be allosteric sites where activators or inhibitors can bind to cause conformational changes that affect enzyme activity.

There are already more than 5,000 biochemical reactions known to be catalyzed by enzymes. Enzymes are also used in industrial and household products. For example, enzymes (enzymes) are used to brew beer, make wine and cheese. Some diseases are related to the lack of enzymes in the body, such as phenylketonuria and albinism. Here are some common examples of enzymes:

• The

amylase in saliva catalyzes the initial digestion of carbohydrates in food.

• Papain is a common enzyme in meat tenderizers, and its role is to break the chemical bonds between protein molecules.
• Enzymes in detergents and detergents can break down protein stains and dissolve grease on fabrics.
• When DNA is copied, DNA polymerase catalyzes the reaction and checks whether the correct bases are used.

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