Why does the cut surface of apples, pears, bananas or potatoes turn pale brown when we cut them? The reason is that some of the chemicals in the pulp components are oxidized to a light brown product, and this oxidation is catalyzed by the enzymes contained in the pulp itself. If we refrigerate the cut fruit or immerse it in ice water, the rate of browning will be slowed down a lot, or it will not happen at all, because the activity of this enzyme at low temperatures is very low, or even completely disappears. Oxidation naturally slows down or cannot occur at all. In addition, experienced chefs sprinkle lemon juice on fruits such as cut apples and pears to prevent browning of the pulp. Because the enzyme activity will be reduced a lot in an acidic environment.

This article aims to introduce the functions, characteristics and applications of enzymes. It is expected that readers who are less exposed to life sciences in general can understand the catalysts in living bodies through this article.

The example of the enzyme action mentioned in the first paragraph may be a relatively negative example, because the browning of the pulp is always unpleasant. In fact, every living cell in the biological world contains many kinds of enzymes. One miracle of life is that hundreds of chemical reactions are carried out in each living cell at the same time. Without enzymes, these chemical reactions would either become too slow or not happen at all, but the chemical reactions in the cells are necessary to sustain life, so we can see the importance of enzymes.

Enzymes are proteins, and they have three main characteristics:

(1) Strong catalytic effect.

(2) They are quite specific to the chemical reactions they catalyze.

(3) Their activity can be adjusted.

Enzymes have a powerful catalytic effect, and some enzymes can even increase the chemical reaction rate by a factor of 1020, which is the most effective catalyst known so far. Enzymes really have a surprising impact on the chemical reactions needed to sustain life. For example, the carbon dioxide produced by the cell's respiration must be excreted from the body, but this carbon dioxide is transported to the lungs by the blood, so each carbon dioxide molecule must be combined with water molecules to form carbonic acid in order to be transported. Without proper enzymes in this step, the reaction rate will be too slow to sustain life. Each molecule of the enzyme (this special enzyme is called carbonic anhydrase) can catalyze the formation of 36 million carbonic acid molecules in one minute, naturally it can effectively remove carbon dioxide. The catalytic efficiency of enzymes, that is, the enzyme activity can be specifically expressed by numbers, called the turnover number. For example, the carbonic anhydrase mentioned above has a turnover number of 36 million.

The special specificity of enzymes is also an important feature. Other catalysts do not have this characteristic. For example, strong acid is a catalyst, which can not only catalyze the hydrolysis of any amides, but also catalyze the reaction of other organic substances (such as the dehydration reaction of alcohol); but urease can only hydrolyze urea. This is an example of absolute specificity, which is an enzyme (with a specific substrate). Some enzymes are relatively specific, as long as they are similar in structure, they can be catalyzed by this enzyme. For example, lipases can hydrolyze any kind of fat. The specificity of enzymes is actually related to its mechanism of action.

Another important feature of enzymes is that their activity can be regulated. Why does enzyme activity need to be regulated? One of the important reasons is that some enzyme activities in the cell are too high, so high that they will not only destroy the structure of the cell, but even the whole cell will disintegrate the powder. Nature's ingenuity has solved this big problem. These active enzymes usually exist in a low activity state, that is, they are stored in the cell as the enzyme precursor (enzyme parent material). Once needed, the "enzyme precursor" will be released to the place to be reacted, and then activated for catalytic action. Various digestive enzymes use this method to regulate activity. For example, trypsin is usually stored in the pancreas in the inactive form of trypsin. It is released to the small intestine when needed and becomes activated after treatment into trypsin--highly active trypsin.

At this point, readers have recognized the three characteristics of enzymes, namely high catalytic efficiency, specificity, and adjustability. Next, let's explore coenzymes. Some enzymes must be combined with coenzymes to be active. Coenzyme is an organic compound (it can only contain elements such as carbon, hydrogen, oxygen, nitrogen, sulfur, and no other elements), and is a non-protein organic substance. Most of them are made from the vitamins we take in our daily lives into. This also shows how important it is to get enough vitamins in your diet! From this reaction formula:

Lactate dehydrogenase
Lactate + NAD + ---------------------- à pyrogranate + NADH + H +

It can be seen that coenzyme NAD + is really involved in the oxidation of lactate ("oxidation" here refers to the removal of two hydrogen atoms). In addition, in the above reaction formula, the coenzyme NAD + is not written with lactate dehydrogenase, which is used to indicate that the combined enzyme-coenzyme complex is actually easy to separate and is not tightly bound together.

Some metal ions, such as magnesium ions (Mg2 +), calcium ions (Ca2 +), zinc ions (Zn2 +), and iron ions (Fe2 +), also function as coenzymes, except that they are inorganic metal ions and coenzymes are organic substances. For example, rennet requires calcium ions to coagulate milk.

The relationship between enzymes and diseases and the application of enzymes in medicine may be more concerned by readers. Many metabolic diseases are hereditary, that is, certain enzymes are inherently lacked in the cell, or the enzyme itself is defective. For example, Graucher’s Disease is a congenital disease in fat metabolism. The cause is a congenital lack of a lipase, which causes indigestion of fat and accumulates in the liver and spleen, causing abnormal expansion of the liver and spleen.

Any substance that reduces enzyme activity is called an inhibitor. Some enzyme inhibitors cause death by poisoning the organism. For example, cyanide ion (CN-) is not only extremely toxic but also has a rapid effect. The reason why cells can use oxygen to maintain their own life phenomenon is entirely dependent on an oxidase. This oxidase requires iron ions (Fe3 +) to be active, and CN- is easily combined with Fe3 + to form CNFe2 +, so Reduce oxidase activity. In addition, the poisoning of heavy metals such as mercury and lead is due to the denaturation of enzyme molecules (protein molecules) caused by mercury and lead, which makes the enzyme lose its catalytic efficacy.

Not all enzyme inhibitors are toxic, and some are good medicines. The most famous example is the antibiotic penicillin. It is an enzyme inhibitor necessary for bacterial growth, so it can inhibit the growth of germs.

Enzymes are also widely used in clinical medical laboratory analysis. Some enzymes are only found in cells, and are not found in blood or other body fluids. However, the normal metabolism of cells releases these enzymes into the blood, but the concentration is always much lower than the concentration in the cells. Clinical medical tests and diagnoses. If you find that some enzymes in the blood are too high, it means that many cells are injured, damaged, or overproliferated (such as cancer). Therefore, measuring the concentration of certain enzymes in the blood has become a very important diagnostic tool in clinical medicine.

Author's Bio: 

Creative Enzymes is a remarkable supplier and manufacturer in the Enzymology field. Equipped with advanced technique platform, Creative Enzymes is able to offer high-quality and professional services for customers. Its products and services are widely used in the academic and pharmaceutical industries.